Well I've been playing it, not bad but not great either. The story and everything I don't much care for...it talks a lot about the complicated stuff that happened in previous games that I don't really remember about, and it doesn't recap it for you so I just kind of go with the flow.
Personally I suck at stealth games and tend to end up running and gunning, which is actually pretty fun in this game. The gun combat has definitely been improved. Stealth is about the same as always, though I haven't gotten to the part with the dogs yet...Missions have little side missions within them, like finding a piece of data or securing a VIP on the most wanted list. You get extra money for doing that stuff which you can use to upgrade your weapons/gadgets.
There are still some silly things, like how Sams goggles still shine bright in the darkness but nobody sees it - and now your suit has 2 green indicator lights that light up whenever you're hidden, seems kind of counter intuitive but of course enemies don't see the lights.
They also kept in the execute thing from the last game, after you get a stealth kill or whatever you can select 1-3 targets and press execute and Sam will auto kill them for you...Makes things convenient, but pretty gimmicky. They also added in the cover-to-cover auto-move like they did in the last Ghost Recon. This I guess helps you stay in cover but having the game automate so much for you makes it feel like less of a game.
Oh and they added a hub of sorts in the form of a super modified plane with a sort of battle map which you use to select your gear, buy upgrades, and select your mission. There are campaign missions, side missions, and multiplayer missions. I have yet to try multiplayer.
As of now the game is still kind of buggy. Almost every time I alt+tab for whatever reason, it crashes. Whenever I change certain video settings I get stuck at a blank white screen, and the game keeps resetting itself to DirectX 9.
All in all it's still Splinter Cell, even if Sam looks and sounds completely different (so do the other characters, like Grimmsdotor or whoever - she's now a hot, seemingly young, nicely bosomed, redhead who's also a CIA intel genius - but I think she's truly in the game for the former, not so much the latter).