Hmmm.

I have - but then I am within one.

There is a difference, I think, between the experience of the individual and what an entire church, etc. does with that experience.

It seems to me that there is often, from those outside a faith paradigm, an assumption that others are within it because of indoctrination, mind control, etc.  It's entirely possible to be part of a mainstream faith because of personal experience.  (I well remember being told by someone that Christians are... distanced from their God and have no real contact.  Pointing out the belief in transubstantiation, and the fact that the largest group of Christians have the experience of consuming their deity, brought the response that "no one believes that" - because my discussant could not believe it).

However, I begin to rant, apologies.  My point remains that it is possible, "even" within the mainstream faiths, for individuals to have what you term spiritual experiences.  (My incipient rant is based on what I have perceived for years as a creeping assumption that contact with deity exists only outside the mainstream...). 

To bring it vaguely back on topic... *IS* there a difference in spiritual experience within and without the mainstream?  Does the fact that 1.1 billion people share at least some of the rudiments of a belief - even in something so "magical" as transubstantiation - mean that the spiritual element is lessened?