I'm a pretty huge fan, actually. At least of the Roger Waters era (1968-ish - 1983-ish). I've never really seen the genius in Syd Barrett, and the albums and tours they made after Waters quit are competent but dull, but... I mean, Meddle, Dark Side of the Moon, Wish You Were Here, Animals, The Wall, that's some pretty fantastic music. Waters' solo albums aren't bad either, even if he's a much better lyricist than musician.
I'm not sure I'd agree that there was anything stream-of-consciousness about them after 1972 or so, though. Roger Waters' lyrics usually read like a half-decent philosophy/psychology text book made to rhyme; there's a lot of reasoning and planning in advance to it, and with the sort of live shows they played - especially the ones they've done since The Wall - there really wasn't a huge amount of space for improvisation. Which is a bit of a pity, some of those early gigs are amazing.
I really should look up some youtube links.