I think it will at least be on par with the original. Most sequels suffer due to lack of a good storyline or repetiveness. Jackass can't really fall to those two problems. As long as they can keep thinking up stupid crap, it will be loved by the people that loved the first one. It's main obstacle to overcome is that Jackass has been gone for a while. It may not be able to garner the same attention.
I took my oldest son to see it last night. The Jackass boys are crazier than ever! I laughed my ass off from start to finish last night. It's not for the feint of heart, but if you've got the balls it's a must see.
I just saw it as well. Some of the stuff made me crack up with laughter, some of it was really disturbing... but overall it's probably one of the funniest movies I've seen. It's a must see for anyone who likes Jackass.