On reflection, one of the things the movie lacked was the fundamental charm that I associate with the Muppets. To some degree, the movie acknowledged this with the Moopet spoof characters. Also, I'm not particularly fond of Amy Adams' acting (I found her downright irritating in Julie & Julia), while Jason Segel if anything overplayed the essential goofiness of his role. So while there were plenty of laugh-out-loud moments, especially with respect to the music editing (in a sort of "the eighties, you had to be there" way), the movie never really gelled for me.
Still, if you're a Muppet fan, it's worth seeing. Go for the matinee, though, or wait for the dollar theatre showing. This movie doesn't merit an evening of your time and full priced movie ticket.