The cameos are insane - this probably sets a record not just for a Muppet movie, but for anything, from Danny Trejo to Frank Langella, Celine Dion, Tom Hiddleston, Lady Gaga and WWE's Hornswoggle, to name but a few. Better than any of them, though, are the cameos by various lesser-known Muppets, from Pops to Uncle Deadly, most of whom get at least one good moment - boomerang fishie thrower Lew Zealand even gets one of the film's best lines.
While it's good that the focus of the movie is back on the Muppets, as opposed to making a human the protagonist, it does lose sight of having Kermit be the main, active hero - for most of the movie, he's in a prison cell, and only develops any kind of substantive plan of action in time for the climax; the rest of the time, he has no concrete goals (to tour? To scold? To make money? He's purely reactive, never proactive). There are enough gags that you may not notice, but the plot really makes no sense at all, even under Muppet logic.
And maybe that doesn't matter, because it's still all in good fun. I laughed at the jokes, but I shrugged when it was over.
Preceding Muppets Most Wanted is a Monsters University short, "Party Central," that's better than the entirety of the movie that spawned it.