I must be in the minority because I don't see what the big deal is over Borat. Granted, I haven't seen the Ali G show so I must be "in the dark" in regards to some of the jokes/character but from what I've seen in the trailers, it's simple slapstick humor.
Haven't seen the flick yet (was supposed to go last night--going next week instead), and I agree that there are some bits in the trailers which look a little slap-sticky (antique store scene, I guess--which looks hilarious to me). But from what other stuff I've seen of Mr. Sagdiyev, the humor comes from playing on the naivety a lot of people have about foreigners--which usually either results in some candidness (uncomfortable for the viewer) or awkward silence, and those types of things don't translate to teasers and trailers very well.
It could go either way for people, though, I guess--depending on their sense of humor. I had my mom watch the OKC segment, and she didn't get it, and didn't like it because he was making fun of unsuspecting dumb people (or people who should otherwise know better). But that was the very reason that my dad ate it up with a spoon (and incidentally, he liked it so much that he wants to see the movie, too).
Anyway, here's a couple of segments I really love (both from season two of Da Ali G Show):
Wine-tasting in Mississippi (okay, so that's somewhat slapsticky)
Learning Country and Western Music (that too)

To me, that's comedy gold, but I know it's not everybody's cup of tea.
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(Where's Franklin?)