A. such experiences are reserved for elites, and thus shed no light on the driving forces behind religion.
B. such experiences are delusory or, at least, worthless. Check out PZ Myers
C. such experiences can indeed be powerfully transformative and may be worth pursuing (Sam Harris).
D. I can enjoy all of these experiences myself without engaging in religious woo. Here, you have Richard Dawkins emphasizing that he can enjoy a sunset (it's usually some celestial phenomenon) as much or more as the next guy.
These categories aren't meant to be mutually exclusive. They're just intended to reflect the dominant responses you'd expect to hear from various rationalist personalities when you play a game of word-association and blurt out terms like "neurotheology".
I've avoided the term "atheist" for my argument. Theravadan Buddhist purists (who often are Westerners re-projecting all that they thought they had rejected in Abrahamic religion) might spurn some of the aforementioned practices as superstitious or "degraded" or untrue to the original scriptures, and embrace others. Here, you get a mix of all the above categories. These Buddhists would probably self-identify as atheists, but might not be thrilled with the geeky "rationalist" tag. Rationalists are not known to seek out the spaces between thoughts. However, in many cases, especially in the West, the two terms can be used virtually interchangeably.
Regarding A), at best it's a simplification to say that the experience of meditation is reserved for religious elites when, even today, a large percentage of the male population in places like Thailand is expected to engage in an extended retreat at least once in a lifetime. To then argue that the religion "in itself" can do without meditation seems rather silly.
I'd like to add my own category E). It goes like this: Yes, these experiences may be worthwhile and transformative, but rationalists can't have them. Or, to be less dramatic, they may be somewhat handicapped when seeking them out.
I recall Phil Plait arguing that he might view the night sky with more awe than less educated folks. With his trained eye he, after all, can make determinations as to whether stars are retreating or not. Their colors tell him something about the heat they produce. He knows their stories. That's very nice, but he's playing right into the hands of the folks who claim that a scientific view dulls the moment to moment appreciation of life. For many, this dunderhead included, awe arises when one is left thoughtless, and dissipates as a conceptual overlayer gets re-established. That's the vaunted Zen "beginner's mind" to which contemplatives aspire, as opposed to Plait's "expert mind".
Blathering about spiritual experiences is a dangerous road, but I've done enough meditative tinkering to know that the quality of sights and sounds that impinge on consciousness are hugely variable. In the Tibetan tradition, you may identify with a "yidam". Depending on the yidam you focus on, your post-meditative perceptions might be altered in interesting ways. Meditate on Tara, and you may find the soft curves of your coffee cup to be unusually prominent and compassionate. Meditate on a heavenly realm, and you may find every object glistening, imbued with sacredness. Meditate on a wrathful deity, and a confident, sharp clarity may be felt. Other times, the world is saturated with a dreamlike quality. There's really no reason to find these gestalts to be any less "real" than that of ordinary, tedious, ego-focused, samsaric vision. But you're not going to "get it" if there's a big internal debate going on as to whether these deities have objective existence or not.
There's a bit of a paradox here. Rationalists identify strongly with the logical, thinking mind ("sem", in Tibetan, if I recall). They believe in its eminence. And yet, they often don't seem to fathom the extent to which this mind can exert its power right down to the level of perception and sensation, where a deity's presence may be felt vividly and organically. "Sem" may be more or less isolated from the realm of the senses for some folks. There are indications that religiosity, suggestibility, etc., may have genetic components. Point is: maybe some folks are simply cut off from certain experiences.
Another Tibetan practice is "guru yoga". Here, you summon up intense devotion for your teacher. You see him as no different than Buddha. It's something that's awfully difficult for me (superhuman authority figures on thrones are problematic, to put it mildly). Rationalists have an understandably difficult time suspending disbelief and logic in this sort of situation, and it's all the more difficult when the supposedly venerable guru figure spends massive hours watching TV, seeking out his next fuck, and micro-managing the financial affairs of the organization. But here in the West we have psychologists who are supposed to free us of neurosis. Imagine, for a second, that you viewed your therapist as no different than the Buddha. You'd probably carry out his instructions especially intensely and dutifully, and results might be quick in coming. Of course, this sort of relationship can and does lead to abuse, but that's another issue.
As far as I can see, these feelings of intense devotion are hugely emphasized in virtually all religious traditions. They enable certain experiences. What object of intense devotion can atheists claim?
Various traditions emphasize the importance of creating an "auspicious" environment to facilitate prayer or contemplation. We might simply be talking about lighting some incense, or we could be talking about a very elaborate ritual. How might rationalists quicken various "spiritual" experiences? What venerated implements are available?
Next, there's the issue of "self knowledge" for rationalists. Being of a scientific bent, they may disregard any information gathered via self-reflection, since it's 100% subjective. In other words, because you believe that you can't probe your mind via the scientific method, you're not even going to try. I say "believe" because I'm not at all convinced that the mind can't be investigated, and subjectivity can't be minimized via the structure offered by meditative techniques. You attempt to focus solely on your breathing, but repeatedly get distracted in discursive thoughts. You then realize that you're not quite as "in control" as perhaps you thought. Is that not insightful? Is this not an experience that can be shared with and confirmed by other meditators? Perhaps Westerners are somewhat burdened by the impression that "self-knowledge" necessarily involves stuff like recalling and playing out the historical chain of events that culminated in a rubber boot fetish. There's also this very Western notion that "self-knowledge" involves selecting out the traits that make you especially different from the next guy, not the traits that bind you.
Rationalists reject views that are not based on sound evidence. That's nice, but 24/7 we're faced with the existential dilemma of constructing/maintaining/abiding-by a self-perception that is based on...what? Many scholars of the early texts of Buddhism remark on the radical deconstruction of self going on in these works. It seems, however, that many rationalists would prefer to avoid this particular exercise in deconstruction. Or, perhaps, they think that Ellis, Maslow, and the like have rendered these approaches moot. Laughable, really.
Rationalists focus on logical and evidentiary errors. But what of perceptual errors? A classic Hindu/Buddhist example is that of an individual whose fear causes a rope to be seen as a snake. Are rationalists less prone to such effects? Perhaps more prone. Mistaking a rope for a snake may occur once in a lifetime, but the unjustified reification of self is near-constant and worthy of examination, according to the Buddhists.
In science, anomalies often spur insight. It's rather odd, then, that an apparently large subset of rationalists have concluded that meditative self-experimentation is necessarily a fruitless endeavor. Science isn't mere application of logic and statistics. It's about going out and finding and manipulating materials and circumstances. No?
Ask rationalists why religion endures and they often unwittingly offer up a sharp reflection of their own cognitive biases: it's there to explain the cosmos. Or, perhaps, it's there to offer a legal/moral/social skeleton for society. For the politically inclined, it exists as an elitist power structure. I'm reminded of a classroom of well-indoctrinated schoolchildren. Ask them why people take drugs. You might be surprised at the sophistication of the responses, but isn't it odd that nobody chimes in, "because drugs make you feel good"?
Folks spend a good deal of effort justifying their own propensities. A musician may pity those who can't "get" Coltrane. For the literate, it's lamentable that some humans never experience the genius of Joyce or Shakespeare. You may be seen as pathetic because you're clueless about the gritty reality of the inner city. Or because you're out of touch with nature. Because you've never gone for a real adrenaline rush. Because you've never experimented with S&M. Because you've never studied martial arts and can't defend your own body. Because you've never been through cancer. Because you've never had children. And of course, you may be pathetic because you haven't had a "born again" experience. Or because you're deluded enough to believe that you've been touched by a sky fairy. And it's pathetic that some folks don't seem to appreciate the diversity of mental states that they encounter in interactions with others.
In fairness to Phil Plait and PZ Myers, they've got awesome, provocative blogs. Plait has indeed spoken of the purely visceral power of heavenly imagery, and PZ, when he's not thrashing creationists (which is enjoyable in its own way), can write incredibly evocatively and lucidly. He's sure as hell not autistic.