It feels better in some ways, and worse in others.  The movement, shooting, etc feels good.  Some of the things they took out don't seem justified though, I'm not a fan of Sonar Goggles instead of Night Vision goggles, it's way more punishing trying to see in the dark than it should be (the black and white actually makes it easier to accidentally walk into the light).  Insta-fail missions and traps, also a big negative.  Also there are a lot of noticeably linear points where the choices are play Rainbow Six, or shoot out 4-8 lights and call that stealth.  Chaos Theory was and will definitely be remaining my favorite, Conviction is competent (I'd give it an 8/10) and definitely better than Double Agent, but in their quest to make the game more accessible they forgot some of the lessons learned in previous Splinter Cells and left a few too many things out.  Night vision goggles, for example, != inaccessible.  Vents != inaccessible.  Disarming traps instead of battling the difficulty of seeing through sonar goggles != inaccessible.
 
In short, making the game more accessible is fine, hell I'm getting impatient in my old age anyways (lol 27), but mistakes in gameplay changes shouldn't be automatically granted a pass under the guise of accessibility.

I just beat the SP campaign I really loved it, thought it was very well done, I am about to play some co-op when my friend comes I never played any Splinter Cell games before because I usually dont like stealth games that much but I thought this one looked more my style and I was right.

I think I got a headache while playing through the one part where you have to  (not really a spoiler) navigate all the invisible lasers by using the sonar googles.

Absolutely adore it. 
 
My problem with the criticisms made? Across the board, critics are arguing that stealth is unnecessary, and 'shooting dudes in the face' (to paraphrase Jeff) is the easiest option. With this, gadgets are apparently useless. I, personally, use gadgets very frequently (with both the EMP grenade and proximity mines being my favourite). Moreover, there's a satisfaction that comes with the stealth that you don't get with a gun. Shooting guys in the head is the equivalent to choosing the easiest option on a JRPG , and mashing X.  
 
The stealth is optional. And to those who argue that there is a lack of punishment for aggressive action  [Joystiq], they seem to ignore the fact that Hunter and Infiltration (in my opinion, the two best game modes) both punish players for going in guns-blazing.