As the other review states, if you're a fan of the Muppets, go see this movie. Now. It will give you warm nostalgic feelings. There are tons of Call Backs and Shout-Outs, and hilarious jokes, for adults and kids alike. The musical numbers, original and old, are good, and it's just a feel-good movie.
That said, the plot is a little weak, but if you're a Muppets fan, or a kid, you can probably overlook the few weak spots and just enjoy the most sensational, inspirational, celebrational, Muppetational movie of the year!