I remembered reading something about it by niniendowarrrior. There's a discussion here:
http://www.gog.com/forum/general/ninja_giveaway/post24113
"It is very far from good. Still-Life 1 playthrough is a prerequisite if you want some portions of the game to make sense. But Still-Life 2's major storyline is very far removed from Still-Life 1, and it is just not good. Puzzles are very pixel-hunty, the story is very weak. Visuals are terrible and the voice acting doesn't fare any better."

LOL, thanks! That whole discussion is an eye-opener!

I played it a year ago. It wasn't hard at all, but some of the puzzles didn't make much sense. If you get stuck, there are some guides on the net that will help you. Also, you can die in this game, and if you do, you have to re-start from a checkpoint. So, it's more like "try instead this thing this time". Not a long game, and with an abrupt ending, I don't recommend buying it full price. But included in a bundle, and with the charity in between, I say yes, get it. The story is kind of interesting. It is based in the comics, which later got a film adaptation in the early 2000's.

3rd bonus unlocked

Does anybody know which DLC exactly is included with P.A.M.?

My steam dlc tab says:
DLC 2 Chaos Pack
Death Arena 8 DLC
DLC2

This.

Thanks! For some reason I thought that the game had more DLC and was worried about buying an incomplete package, but it seems that this is the only DLC for the game (Steam doesn't sell any other DLC for it, at least).

your avatar is like a very slow stop motion film these days...

Very slow and very poor...