I finished Magicka's single player campaign last night. What a great great game. It is innovative and funny and challenging and chaotic. Most of all it is tremendous fun.
The game really does need a mid level save facility though. The single player game is very challenging particularly when you start out. Having just finished I also really wish I could select a chapter to replay without having to start again from the very beginning.
Happily I didn't encounter any serious bugs in the single player adventure but I did have two serious crashes in only an hour of multilayer.
Apart from the crashes my brief foray into multiplayer was enjoyable. Pressing the instant game button, I joined a random group for two of the middle chapters. Even with an uncoordinated group of strangers the multiplayer game is a good bit easier than single player as long as every one remembers to use the spammable resurrect skill regularly. You can just nuke everything and rezz everyone after the inevitable friendly fire deaths. Indeed the lesser challenge of multiplayer means that I actually enjoyed the single player game more. That might change if I was playing with friends of course.
Criticisms aside though let me firmly state that this game is a a masterpiece. A flawed masterpiece certainly but a masterppiece nonetheless.