I really enjoyed this one too. It's a complete mindfuck that doesn't make a whole lot of sense most of the time, but they really nailed the 70's vibe.
I've only seen it once though, so perhaps elements of the plot make more sense on repeat viewings. I'd definitely watch it again.
"Through unlit corridors of purest oblivion.
Submerged in a sea of darkness without end.
To feel nothing...hear nothing...for a thousand eternities." - Evoken - Quietus