My stab:
Overrated on this site:
Pasatiempo - crowded routing on front nine and mediocre 6th, 7th, 8th, 12th, 13th and 17th holes. The first two par threes on the front are wonderful holes but almost identical. In the winter, the course has been a bog whenever I have played it.
New South Wales - Beautiful site, mediocre 2nd (par three), 3rd (dogleg left par four), 4th (I can't remember it), 5th - beautiful hole but basically a short par five straight over a hill, 10th, and 18th. I cannot remember some of the other holes so there may be more.
Underrated on this site:
I agree with TPC at Sawgrass. I was surprised at how enjoyable the course is.
Classic at Maddens (Minnesota). - I think it is one of the best in the state - despite being tough and penal in some places. Reaction on this site has always been lukewarm among the few who have played it.