I've used K on one or two occasions (after-prom party my senior year, and once other). I never found it to have any
psychedelic quality - it actually feels remarkably like being drunk, but without the related ill effects (i.e.
nausea and
hangover) Ketamine does have a slightly more mellow quality to it than alcohol - it's not that you're too drunk to get up and move around, you just can't be bothered. This feeling is pretty well-documented, and called the
K-hole.
I agree with nutate that ketamine's no mind-expander. But it's great for chilling, preferably with some friends.
Be warned: you will not be motivated to do anything at all, for pretty much any reason, while under the influence of this drug. I distinctly remember that I couldn't be bothered to reach for the remote when a shitty tv show came on.