I finished Alice: Madness Returns. According to the game, it took me a bit more than 16 hours.
I like it better than the first game. Art direction and level design are fantastic (you won't find a more creative and beautiful game released this year), voice-over and story are as good as the first game. Tone & atmosphere isn't as dark as the first game (understandably, considering Alice mopped up Wonderland pretty thoroughly in the first game), only right before the end it becomes really dark, perhaps even shockingly so. The ending is ambiguous enough that it may warrant another sequel.
Music is not as memorable as the first game from what I remember, although I really like the main theme (very Arcanum like).
Combat is better, there aren't as many enemies and weapons as in the first game, but this time around you need some strategy to beat them. It can also be pretty challenging when facing groups of different enemy types (although when close to death, there is a limited win-button in the form of Hysteria, when Alice will go nuts for a short time, becoming invulnerable and doing massive damage).
Overall, 8.5/10.
The game also has PhysX and 3D Vision options, which I imagine make the game look even more impressive than it is, but I couldn't benefit from this due to my computer sucking balls.