Ah, I can't help but spur on the psychedelic talk a bit, though it is inherently (at the bottom of the spiral) something that cannot be communicated (by its nature), and certainly can be known only experientially, though all these 'fingers pointing at the moon' I find interesting, especially hearing other people's analogies. It certainly magnifies whatever you bring into the trip, and I find that if I enter it with an attitude of acceptance and submission then I allow the acid to create a much more profound experience, without my interruption. When it reaches zero kelvin and enters into that silence-of-silences, that complete letting go of all ideas/emotions/concepts, without reflection or the desire to communicate the experience, even to oneself- that's when it borders on the spiritual and earns its entheogenic classification.
I usually relate to a sinking analogy, with non-lucid life being the sloshing current on the surface (characterized by being rooted in the thinking mind), and acid acting as a catalyst to bring these energies to a still point, almost as if there were something like gravity pulling me down to that place-that-can't-be-expressed. I'm sort of a religion geek, so I'm always interested with the striking parallels between these experiences and concepts like Nirvana and the Kingdom of God (Huxley called it Moksha Medicine, after all). I personally like 'the Riverbed', 'the Substrate' or 'Chu', though there are as many analogies for trying to communicate it as there are communicators. I like that Joe mentioned 'riding the wave', that's another feeling I sometimes get. No tension or resistance, just flowing with it, completely in-tune, almost like a needle finds a groove on a record. The whole 'purging/pouring out' thing I can certainly relate to as well. There a link to McKenna's concept of 'the dome' ?
As far as visual stuff goes, I had a somewhat opposite experience a few times, where, when looking at an object close to my eye, the view retains its fish-eye perspective, and my mind doesn't 'unfold' it and make sense of the view by reconstructing it without the extreme distortions. Usually the only visual effects are of course the vibrancy of the colors and the way that everything 'breathes' and flows with a certain life.
It does feel a strange thing to discuss in a public forum though, these are pretty intimate and personal experiences after all, something with an almost sacred air. If only there were a washed-out psychonaut subforum...