This video made me finally get around to playing the original Stalker today. I must've played it for a couple of hours or so. Really liking it so far and, unlike my first attempt to play it, it's been completely stable. I guess some combination of the game, graphics driver and Vista updates over the months since it came out all made a difference.
I did still notice some stupid errors during the opening tutorial section which give you a bad impression of the game when you've only just started playing it. Stuff like the trader talking to you when his lips aren't moving, or his tutorial speech samples cutting themselves off when one plays before the other has finished. Or the rotating circles indicating where to click on the PDA not always being in the right place (widescreen monitor issue maybe? most of them were in the right place, though). After that, though, it's been totally fine.
Still trying to decide whether or not to install the Float32 graphics mod or just play it as the devs intended.