I've just completed Stalker for the first time. I'll try not to stretch this post into a review since Tricky said most of it.
I really liked the game. It stands out as a shooter as well, but the RPG elements really add to the game's depth, especially the inventory management. I can't describe how good it felt to have finally encountered a shooter (despite the RPG elements, Stalker is still mainly a shooter) which pays such attention to the player's inventory. Also, the game has multiple endings (seven, if I recall correctly), so if you get a mediocre enging after your first time through (which is inevitable, since it depends on how much money you have, and money is really easy to get in this game - fortunately, this balance issue has been fixed in the patch), don't sweat it.
The atmosphere is simply fantastic, be it huge open areas with rusty car wrecks and abandoned villages or old Soviet underground facilites, this game does an outstanding job in providing a post-apocalyptic feel.
Also, as Tricky stated, the game reminds of Fallout on more different occasions, which really can't be bad. *mild spoiler*
Not to mention a great hommage to F2 - a Gauss Rifle that uses 2mm ammo, hehehe.*spoiler end*
The game has its glitches, but I'll quote one of the NMA members (he'll recognise himself if he'll ever be reading this, hehe) to shorten this paragraph -
Bugs can be fixed, but ****ty design is forever. Stalker, obviously, has the former but lacks the latter.

In my opinion, this is one of the best games in the last several years. I'd even be so bold to put it in the same category with games such as Deus Ex and System Shock 2 (despite Stalker's lack of character development), but it's still too early to tell.
Heh, it seems I've stretched it a bit too much. Ah well.
