"Watching it last night was like stepping into a timewarp. And, as much as I admire the movie, it wasn't a very pleasant experience. The endless pontificating, chasing meaning in shadows, the illusion of depth, the blurred line between muttering, shoe-gazing, time-wasting stoners and the truly mentally ill..."
Good summation. I've only seen it once as well, shortly after it was released.
And what I think is really un-nerving about it, if not outright unpleasant, is that we don't really know what we're supposed to make of it all. I mean, it's clear that in Easy Rider, we're supposed to admire the youthful outcasts, and in Clockwork Orange, we're supposed to dislike them(at first, anyway). But with Slacker, it's like you don't hate these people, but you don't really love them either. And even in the funny parts, it's not always clear if you're supposed to be laughing at or with them.
Like you say, a timewarp, and I'd say maybe a social document(if that doesn't sound too pretentious): "This is what it was like in the late 80s/early 90s, among educated-beyond-their-station young people in a typical American artsy/college town. Take it or leave it."
Uh...what was the question?
Schrodinger's cat walks into a bar, or doesn't.