There's a couple of reasons. First, the movie's DAMN fun. I haven't laughed this hard at anything since the first time I saw Rat Race in the theatre. This is just as bladder-bustingly funny. You do have to be ready for some absurdity, but I think you saw that in the trailer.
Second, this weekend is the trial run. It's where Mirimax will determine how much of a wide release, if any, the film warrants. So the three cities it's showing in on Friday (New York, San Francisco, and Los Angeles) could very well be it, since this is the kind of movie that depends on word of mouth to get the snowball rolling.
Third, it's a good excuse to get to the Arclight Cinemas. MAN, I can't say enough about this theatre. But for now, I'm not gonna say anything about it. Check my past entries or ask if you don't already know.
Fourth, from what I hear, it's far better than the original. Only one joke is set up better on the DVD than on the screen - every single element other than that was an improvement.
The one thing to be aware of is that you shouldn't be fooled by the trailer. The decision on whether to dub or subtitle the movie was the main factor in it being released so darn late (according to the Mirimax guy we spoke with last night) - they kept changing their minds and going back and forth with it. So the trailers are dubbed --- but the movie itself is subbed. Very worth the effort of reading, though.
All in all, this is one flick / moviegoing experience you pretty much can't go wrong with. HIGHLY recommended.