my 2 weeks old 2011 mbp "7" key is dimmer than the rest but i figure is too much hassle returning or swapping it. so i live with it. for your case, i think u should replace it or get it fix.
no machine is perfect even from apple. mine came with dimmer "7" key and backlight bleeding on bottom right but not obvious compare to my old 2010 model, it was perfect in every way.
it hurts when i pay so much and need to roll a dice in getting a perfect ones.