The opening NPC battles are now much more solid, with waves of Clear Sky consistently heading out into the wilderness to capture points across the swamps. The Steam version, which I've been playing, is at the latest 1.5.08 version, in which most of the game-breaking bugs are fixed (although reported some minor crash bugs remain), and much of the AI tweaked. The first thing to remember is that Clear Sky has been heavily patched since release. The problem for me, however, was that the Stalker I wanted to return to wasn't an augmented Shadow of Chernobyl, but a fixed Clear Sky, which I hadn't played since the pre-release review version. (And that means grenades, annoyingly.) Oblivion Lost is, given the difficulty of combining and over-writing various Stalker mods, a worthwhile download - but it also completes Shadow Of Chernobyl on a profound level. It isn't to everyone's taste, especially since the list of changes is immense, but it includes drivable vehicles, sleep, alcoholism, and reworked NPC behaviour. It's a comprehensive, colossal piece of compilation modding, much of it done by the author, and the rest factored in from across the community. For Shadow Of Chernobyl there's pretty much a one-stop shop for changes, which is the extraordinary Oblivion Lost mod.
The past week of my gaming time has been dominated by Stalker mods: downloading, testing, crashing, deleting, reinstalling, and even a few hours of playing.