I am glad I'm not the only one who has noticed this. I posted about this here:
http://discussions.apple.com/thread.jspa?threadID=2770161&tstart=75
and got no feedback at the time.
I exchanged my 13" MBP i5 for a 13" i7 (they were out of the i5 and I would have had to pay a restocking fee if I just returned it -- thanks a lot Microcenter). The new one is perhaps less yellowish, but it is definitely not as bright (or white) as the 2010.
I, too, suspect this is a problem with the integrated graphics. What a terrible idea it was for Apple to switch from a discrete graphics card!
When you pay top dollar for a laptop, you expect to have a superior screen. This is most definitely not.