Oh look, it's a bundle with Psychonauts, Amnesia, and the over average payout game is Bastion. If you don't own them, you've really got no reason not to purchase this one. It reads like a hitlist of must play games. Only two weeks though, so decide for yourself quickly or it'll be gone.
I already own most of them, and here's a quick summary(really quick, I'm in a rush to do a lot of stuff today):
Bastion - fantastic isometric fighting/exploration game with a heavy emphisis on telling a story to you while you play, often with the occasional comment on how you are playing through it, instead of having cutscenes that force you to sit back and watch. Also contains a really good ending that can leave you with quite a bit to think about while still closing the story proper. Well worth the extra cost to "unlock" it in this bundle. My full review is here:
Limbo - Haven't played it myself but have seen my brother playing segments. Looks basically really creepy and hard, but with ample checkpoints. It's the kind of game that kills you a lot, and has some really creepy visuals, as it's name implies.
Amnesia - Only one of the best games for suspense kind of horror ever. Reason I haven't reviewed it proper is because I can't bring myself to play through it. It's a little TOO good at making a very opressive, scary level while really 90% of the time nothing is even there to kill you. (It's that 10% when stuff IS there that will scare you silly.)
Psychonauts - Needs no introduction. Great platformer/adventure game with some of the most memorable characters/environments/cutscenes/dialog/everythingelse in video game history, period. Reasonably clean language, but some of the later themes for the levels may be cause for the parents to watch closely over what the game shows. (one particular level is the mind of a child who was basically abandoned to an orphanage, and then found out the orphanage is a front for child slavery, it's presented pretty cartoonily in the game but the hard truth is still explained and pretty deep.)
Can't speak up for Superbrothers myself, but from what I read it seems decent enough. I don't own the game to comment.
But in short, go get it! This bundle is awesome, and a great way to support the developers and charities involved! And of course, since it's a Humble Bundle, you can select exactly how to split your payment and how much you are willing to spend total.