I've heard that Magicka itself isn't that long, but it's really given length by its DLC, and that's how they make most of their money. I haven't heard anything past that, but if I get Magicka the game, I figure I might as well go ahead and get the whole pack.
--
Xbox GT/PSN name: TatteredUniform - SSBB FC: 1891-0831-5747 (TEETS)
http://card.mygamercard.net/nxe/TatteredUniform.png