Okay, I have to take back part of it, but certainly not 'overall' - the later part of STALKER and the ending I was a bit disappointed with. The earlier game is definitely in line with what STALKER should be - a hack-and-slash RPG except with FPS combat; the later part of the game (a large chunk of the map but a tiny chunk of gameplay) indeed turns into a straight FPS, and rushes you along a fast track to where it wants you to go. Alas, no scenic wandering of the Zone for me.
Also, no spoilers, but the ending had rather ticked me off. Knowing Russians made the game, I knew they'd pull something odd, but damn it! - even with me being a most patient player, I have to admit I'm too pissed off to see a substance to it right now.
So, as a Diablo-with-guns it passes well, and to me the unforgiving gun modeling and long raids for loot made it quite satisfying, along with staring at scenery. That part of the game is

, bugs and all. Later, ehhh.?? It's no Half-Life, and I wish it hadn't tried to be. I can see myself playing through it again after the many patches one should hope for, though.