Graphically speaking -- in my opinion -- it's more like vanilla Stalker if I had to do a comparison. I don't recall much in the way of eye-drooling candy, but it's far from bad and fit the theme well enough. Just don't expect Crysis graphics out of it. I want to say my biggest complaint was some low resolution textures
I never did get too far in the campaign. For some reason the game felt a lot clunkier than Op Flashpoint, and there were various scripting bugs and weird, unexplainable bits of AI.
The tutorial was impossible to finish for me, for example, as whenever I fired the AT weapons against the dummy tanks, the OpFors would trigger and kill the instructor. My temmate's AI would sometimes have them run into a wall or a corner and just sit there, bolt off to who knows where, or looking around for enemies that didn't exist (maybe that was a feature? panic in combat and all that).
*shrug* It just didn't give the same feeling that Operation Flashpoint did. I never tried the expansions, though, nor some of the more recent patches so your mileage may vary. I played it for a while, but got tired of the game's oddities and its relatively poor performance on my old system, so haven't bothered to get around to playing it again.