Are you familiar with Harris/Dawkins/Hitchens? I'm asking because you really sound like them. Now, let's have a look at what spirituality means according to wikipedia:
"There is no single, widely agreed definition of spirituality.[11][12][note 1] Surveys of the definition of the term, as used in scholarly research, show a broad range of definitions[10] ranging from uni-dimensional definitions such as a personal belief in a supernatural realm[5] to broader concepts such as a quest for an ultimate/sacred meaning,[7] transcending the base/material aspects of life, and/or a sense of awe/wonderment and reverence toward the universe."
It seems, one way or another, that "spiritual" people do not deny the sacredness of their worldview, hence my suspicions when the agnostics (and the atheits for that matter) refer themselves as spiritual. I get the point that spirituality is not dogmatic, more experimental, more inclusive but there's still this notion of the "sacred" intrinsically linked to their beliefs (which is certainly true for all spiritual persons I know of, bar none). Some atheists (new atheism movement) would acknowledge some experiences as "spiritual" which is kind of wacky coming from a stricly materialist, deterministic viewpoint (which is absolutely what they stand for). Indeed, if the whole experience of listening to Bach can be explained in terms of synapses firing, neural pathways and dopamine, qualifying this kind of experience as "spiritual" is just preposterous.
Anyway, enough of my ramblings. On a side note, have you ever heard of Ken Wilber's work? I highly, highly recommend his new book "The Religion of Tomorrow". Wilber makes a distinction between mythic-literal religions (which are those you loathe, and for good reasons) and the trans-rational ones embodied by some the mystics of the great traditions (i.e. Zen, Dzogchen Buddhism and Vedanta). I know more and more scientists are interested in those, especially since the rise of mindfulness meditation. It's a dense, thick book (more than 800 pages), but it's well worth the time and investment, especially so for the agnostics out there!