Alright. I just got done with the tutorial (mission 1).
First of all, I'm playing on an iPod Touch 1G (can't wait to buy the Touch 3G, hopefully this month!) and overall it's pretty smooth, with some slow-framerates only when entering some new areas because it loads textures and whatnot, but even then it's pretty smooth. I have yet to play on 'real' missions, so I can't say this will be like it all the time. Then again.. who uses a 1G yet?..
The sound quality is quite good. Weapons sound good enough, the voice acting is quite nice and the music fits the mood perfectly. It's not an amazing soundtrack maybe, but it's not annoying at all.
The controls are fine, but I noticed the cover I use for my screen makes my finger get sticked to it more than I'd like, and sometimes I can't move around smoothly, but I fixed that with the sensitivity all the way up to 3/4th or a bit higher. I might even go for a higher sensitivity later.
Graphics wise.. well, all you have seen images and videos already. Probably one of the best looking games for iPhone currently. And as I said, even in 1G moves smoothly, can't even imagine how well it must work on a 3Gs. Textures are quite detailed, specially for the ground (if you look straight at it). Actually, if you get close to any object, the texture quality will improve and it can reach quite high levels. Of course, not current gen quality (durr), but much much better than anything on PS1/N64.
Other than that, if you don't keep paying much attention to the graphics, you won't notice anything wrong ever. The only things I've noticed (and I usually look around for all kind of things design-wise) are stuff like, in the first mission when you get down from the chopper you can see the 'limits' of the stage far away, some texture's alphas are a bit blurry hence making the object look a bit weird, but even that isn't really that bad.
The game itself is pretty good. Quite like COD4 in most aspects. The game also helps your aim a bit which sometimes is nice, but I have had a couple times where I were pointing at the enemy and didn't hit him. But still, most of the times it works perfectly.
Anyway... I'm not used to doing reviews so I don't know what else to say. If you wanna know anything go ahead and ask.
edit - alright, scratch that. There are some slowdowns on the Touch 1G when fighting against 3 enemies at the same time (the most I've seen yet). It's not nearly game-breaking and it only happens for a bit, then it goes back to normal.