Starting off, you have nothing but your fists to protect you and to quietly incapacitate unwary guards. The stealth is incorporated extremely well, and the hand-to-hand fighting is extraordinary, though the controls could be a bit smoother in this area.
CoR is very original. I haven't experienced anything like it in a game. I got a similar feeling to when I played the original Half-Life (and the sequel, for that matter). It's full of memborable moments. One such moment is when I snuck up behind a guard who was standing on the edge of a concrete drop, expecting to execute the nifty "sneak-up-and-choke-hold-then-break-his-neck" combo. When I went for the attack, Riddick instead simply nudged him off the cliff. I watched the guard flail and scream as he plumeted to the concrete far below and bounced in a very satisfying way.
The graphics are amazing. It looks like it robbed the Doom 3 engine (and I thought it did until I couldn't find any credit given to Id Software anywhere). But be warned - also just like Doom 3, this is a serious hardware killer. I'm playing on an Athlon XP 3400+ equivalent with 1Gig DDR400 and a Radeon 9800 Pro 128mb. To get a playable frame rate with shadows and a little AA, I had to play at 800x600 with everything knocked down to half.
Quite simply, this is an immersive experience worthy of playing. Only a few bugs and control issues are what keep me from rating it higher.