Just completed this, thoughts below
+Graphically fairly impressive
+More ‘fun’ than some earlier titles in the series
+Executions and violent interrogations make you feel pretty badass
+Decent storyline (although it feels like a bit of a Max Payne rip-off at times)
+Nice change of scenery for the military level in Iraq
+Writing on the walls, video flashbacks etc are done well
-Bizarre performance, I first tried playing this on my i5-750 @ 3.8 but gave up due to low GPU usage, assuming I was CPU limited. Having upgraded to a 3570K @ 4.5 I decided to give it another bash but it still performs sub-optimally, frequently dropping under 60fps and occaisionally as low as 37. What I find strange is that GPU Usage, VRAM usage, CPU usage (on any core) and RAM usage are all under 100% so there doesn’t appear to be a bottleneck! Google suggests I’m not the only one to experience this.
-Awkward controls in places, I preferred the old system of cycling speed with the mousewheel to the run toggle (which is hard to know whether you have it on or off when crouching)
-Pulling people over ledges is very contrived
-Execute lets you shoot people through walls

-Sam’s aim seems to have deteriorated a lot in his old age, you can empty a clip at a bloke 15 yards away and not kill him
-Annoyingly keeps changing my loadout when I don’t want it to – if I’ve bought all the upgrades for one pistol why revert me to a different one after a cutscene? Doubly annoying if you are used to being able to kill with headshots and then your pistol gets replaced by a peashooter. It also stole a silenced MP5 off me in the space of going up a lift to the 3rd Echelon reception area – you start the mission with only pistol but there is a stash right by the start where I grabbed by mp5.
-Rewards system is a bit flawed e.g. “kill 10 enemies with a single clip” is very hard because I am a habitual reloader as per, er, every FPS game from the past 15 years, I do it without thinking so it breaks the chain.
-Cutscenes sometimes run outside the game engine meaning 30fps only – really jerky
-Unskippable in-game cutscenes at the start of some checkpoints (e.g. talking to the 3rd Echelon receptionist) – very frustrating if you die and have to watch the same thing over and over
-Level design is primarily linear, there are a few sections where it snakes you through a few rooms using contrived blockages, even though your objectives is pretty close as the crow flies
-Gunsight upgrades can in some cases be counter-productive, the sensitivity is way too low when zoomed in making it virtually impossible to track a moving target at anything other than long range
-Appalling DRM, I have a slow internet connection (3.5mbit IP profile) and had to pause my downloads while playing to avoid the game being periodically interrupted saying I’d lost my connection to their servers. What makes it even worse, is the game automatically resumes when the connection is restored, so lets say I tab out or go somewhere to try and sort out the connection, I could come back and find myself lying in a pool of blood.
Although I’ve listed a lot more negatives than positives, I actually thought the game was OK overall, one of the more enjoyable of the series as there weren't really any sections that felt like a chore. I’m not sure how well it will appeal to diehard SC/Stealth fans though, as a lot of sections can be Rambo’d.