Cryostasis: The Sleep of Reason has a long history of being on sale. In fact, this current GOG sale isn't even the lowest it's been. Once, it was even free. Funny enough it's part of the "Russian" sale, though it isn't quite Russian (the publisher is), but whatever, I guess it's about a Russian.
Anyways, if you haven't played it yet and you've always been curious, now is another great time to try it out with relatively little risk. Dave, as you probably know, loved the shit out of this game. Some of our reader reviews aren't quite so nice, but all in all I think this game's reputation has seen a nice up-swing (maybe all them sales had something to do with it). It could be real janky on your PC, but again, 4 bucks. Here's the classic Dave-Ryan-Vinny Quick Look.