Also use MRoogle for similiar threads, which may be plenty already.
is it noticeable? i read one thread where the guy compared his old 15" to a new one and said he couldnt see a difference reallly.
I've had both and yes it's better but it's not a big difference. If you don't do things where you color calibrate the screen, then it won't really make much of a difference.
Post pics if possible...
Is it noticeable if you look at them side by side or only if you're doing really graphics intensive work and keep the screen an inch from your face?
I looked at the late-08 MBP at Best Buy with a 9CA4 screen and then went to the Apple store and saw the new one with the 9CA3 screen, and to be honest they looked the same. Both were somewhat cold in color (blue/purple tint). Then again I'm used to CCFL displays (2707WFP and 2007WFP) which tend to be more warm (yellow tint) compared to LEDs.