Short answer: Yes. If a multiplayer tower defense game with third person action RPG trappings sounds interesting, Dungeon Defenders is that and you should buy it.
Long answer: For some reason I occasionally get people asking me if Game X is any good, especially if I have the Steam Community logged in while playing something. I don't know why anyone would ask me, I play all sorts of random crap!
But never have so many people asked after Dungeon Defenders. There's been a few questions on Twitter and a few via Steam Chat and rather than answer any more individually... BLOG POST.