Okay so I'm waiting for my 15" C2D MBP matte screened base model to arrive anyday now but when you see so many posts concerning problems you got to stop to think for a while...and to ask too.
I have a brand new C2D Macbook Pro. It has no uneven lighting issue at all if you have the LCD positioned so it is perpendicular to your eyeballs. I really believe that, in the majority of these "complaint" cases, it's just a question of the user not adjusting the LCD correctly. (oh and FYI both speakers are fine, I don't hear any whine, and it's not overly warm when I have it on my knees).
The other thing to remember is you have to take anything like this with a grain of salt. There can certainly be very real problem reports (e.g. 1st gen Aluminum Powerbook LCD white spots); but forums tend to disproportionately favor whiners and people with unrealistic expectations. The problem is the signal to noise ratio is very low. With all the people complaining about this, that, and the other thing - and a few people endlessly reposting the same complaints over and over - any real problems tend to get buried in the noise.
Bottom line: If you are genuinely concerned, go visit an Apple retailer and look at the LCD for yourself. If you think the screen backlighting is uneven, try repositioning the LCD to see if it solves the problem. Then you can decide whether or not you want to buy.
Edit: The one "complaint" I have is the keyboard does not seem to be as responsive as my Powerbook's was. I have to type a little harder; otherwise an occasional keystroke will get missed.