Thanks for mentioning that. At the time I got my MBP I was really worried about trackpad rise and there was no one else mentioning the same issue but I checked my unit carefully and saw no other signs that would worry me and I did not want to take a part in the display lottery again as my current unit happened to have very decent display which is rather rare with my usual luck.
I'm glad I decided to keep it and I can say now after 5 months of use that it has not gotten any worse or different at all, so probably the trackpad is not just adjusted evenly during manufacturing and I think they all might rise a bit when heating up but it is so minor it is nearly impossible to notice unless the trackpad is even with the chassis in one corner line in my machine. I could not notice it with my fingers on other 3 corners but I have used some other methods to estimate height and it rises evenly on every corner. Just that highest corner can be noticed normally as it starts just below the chassis level and gets just a tiny bit higher when warm, so I can feel it with my nails. Anyway, rise is so tiny that it does not seem to touch the display when the lid is closed, so it is harmless. Also since the trackpad surface is glass, it is nearly impossible to notice visually.
However, I have noticed that you rarely see demo units with uneven trackpads. They are perfectly recessed usually in all corners.