I really can't stand Tim and Eric. I guess I just don't get them. I generally find the things on Adult Swim funny / entertaining, even ATHF (which is also an acquired taste), but I've never understood the appeal of Tim and Eric.
But I'm sure plenty of people feel the same about the British shows like The Mighty Boosh, Look Around You, and Garth Merengi's Dark Place, all of which I find at least fairly amusing.