I just received my Incredible and I had a nice yellow discoloration about the size of a thumb print in my lower left hand side of the screen. I tried running a video for an hour max brightness and it made it darker. Sadly, I returned it to Verizon and went back to my Nexus.
XDA has a thread with same problems, but I figured I would start one here since this is where I go every day.
I've noticed a very mild discoloration in my upper right below the camera. It's very very hard to notice, but after reading this I notice it more now. I would be very annoyed if something as simple and standard as an LCD screen was defective.