This game is a whole lot of fun. I picked this up over the holidays and had the opportunity to ring in the New Year (alright, the day after the new year, but whatevs) by GMing The Mighty Six for my group. I've played a few different superhero games and this one has landed square at the top of my list of favorites.
Character creation is pretty easy, and you're offered an incredibly robust selection of superpowers to choose from. Basically, if you can think of an awesome concept for a hero, you can build that character in Mighty Six. You could easily run anything you'd like, from world shaking titans to noir pulp detectives with little to no special abilities. The art (which is superb and very comic-y) and overall theme the book presents are straight out of classic four-color comics, and there's plenty of humor spread throughout, which is a nice touch.
The game provides a good introductory adventure with some sample characters, but the world building is fairly sparse, relying on player and GM imagination to do the real leg work. Personally, I like this approach as you're not constrained by the game's universe (and I mean, really, it's a supers game. If you can't make stuff up on the fly and have fun doing it, stick to VtM).
There does initially appear to be some crunch to the system, but in reality it's quite simple. Easy to read tables are provided throughout the book and once again in the back, and are invaluable for when you need to calculate massive damage or lifting (with necessary totals running all the way up to The Milky Way - lift with your knees, kids).
The biggest flaw is that there are no bookmarks in the PDF. It's a small complaint though, as there's an index and you can print off necessary pages as you like. Seems like an oversight from a rookie publisher, but considering the rest of the product it's easily forgivable.
I'd honestly recommend this game to anybody, but fans of superhero games and comic books in particular.