The PSL has a stupid thin barrel, and they do string vertically as they heat up IME.
My first PSL was hand-picked out of a dozen, had gorgeous blonde furniture, and was darn near MOA. Then I got the recall notice for the 3rd hole thing. The replacement was a POS. Ugly, mismatched furniture, rough internal parts, crappy trigger and was closer to 3 MOA. I sold it, probably won't have another.
At ~$1,000, I don't know that I'd cal them underrated. They're pretty much the most expensive milsurp out there, save for sniper models or those with a specific, particularly collectible mark, feature, etc.