The review was pretty except for two things, the First was the AA part, I don't know how many ticks on the AA bar you had to slide to get AA, but I can tell you that my HD 4850 with the AA bar maxed drops about 4 fps lower compared to no AA.
The other thing is obviously you guys didn't play the game very long without taking breaks if you're saying this is stable. Because frequent Crash-To-Desktops, X-Ray engine crashes, BSODs, and corrupted save games (Quicksave and Autosave are affected only) are not uncommon. By the time I reached Yantar I was only using quick saves and I had a bugged mission with Lefty's group, basically lost about 5 hours of game time using an older save. On top of that performance starts to drop a lot after some time and I have to exit to windows and start the game again for it to work properly.
Normally I wouldn't cope with these many issues on a game, but it's STALKER, my absolute favorite game series, so I can't stop playing even with all the errors and bugs, because to be honest... it's worth the grief.
Also commenting about the difficulty, to be honest the only thing I find irritating is the excessive power and use of grenades, but I find the game challenging enough for experienced shooter players. I'm playing on Master myself and I have to reload quite a bit to get past even the dumbest places (thank grenades for that), but after you get a decent suit and a slightly accurate gun it's a lot more enjoyable. (Don't go above easy difficulty if you're only a casual FPS gamer)