The game is awesome. It's still Splinter Cell. Its a faster, more energetic Splinter Cell...but there's nothing to fear about it becoming Gears of War, the name of the game is still stealth.
I've enjoyed the CO-OP, it's what I've most played so far. The maps are nice and challenging, because I get my ass handed to me in some sections. I missed out on the CO-OP fun of Chaos Theory, but it certainly feels like the Co-Op experience I'd heard so much about is perfectly re-created with Conviction.
Deniable Ops is just a ton of fun. It feels like it's the Splinter Cell equivalent to the MGS VR Missions. Being able to customize your avatar is a great way to personalize them, and allowing players to go split-screen, online co-op, or solo is a no-brainer...but I've seen enough games that fail to do so, that Splinter Cell Conviction deserves a medal just for having so many options open.
I'm still playing the story, on normal for now...I'll go realistic on my second playthrough, but the arguments about it being only 5 hours are very misleading and wrong, I think. The game can easily be twice that, if you take your time and try to ghost most of the levels. I've enjoyed the mixing they've added too, like the Iraq level. That was a fanastic stroy-telling device they used for the level. The story is really great so far, and pretty intense. The first meeting with Grim at the start...is a pretty intense scene.
You know, it's probably worth mentioning that the complaint of the story being too short has been one that I've heard tossed at Double Agent and Chaos Theory, which I disagreed with as well.