This movie was non-stop fun. The only "problem" is that when it's over you still want more; the two+ hours goes by at warp speed. Everyone in the theater cheered as each favorite character made their appearance, it was kind of like the cheers when the new Enterprise was debuted in the first Star Trek movie.
And you don't just have to be a Trekkie to enjoy this film; my girlfriend had just as much fun and she hadn't ever seen the original series or previous movies...
Obviously it wasn't made by the same team as the originals, and the style/flavor is completely different. Steve Martin really didn't seem natural in the role. Maybe it's good for people who've never seen the Peter Sellers films, but for me it was a letdown.