Will do a full review a bit down the line, but for now:
The single player, funnily enough, might as well be Madworld 2. That sucks, because I didn't like Madworld, and a lot of the same problems are carried over. The campaign is short, but requires you to replay missions to get an arbitrary number of points to play more missions. It's unsatisfying and anticlimatic, and if you want every character without getting an obscene multiplayer rank, you have to play it twice over. Not recommended for solo artists.
The multiplayer is great, though. Pretty much brings Power Stone and a bit of Smash Bros. into the full 3D space. Wide variety of characters, hectic combat, a decent amount of depth balanced with a control scheme which is easy to get into, and a variety of modes. Netcode's solid, too. At half price, it's an easy deal if you're into unconventional multiplayer.
EDIT: So here's a review of Anarchy Reigns.