ANY car is as reliable as long it has been taken care. There is no car out there that will last long if neglected. Being that is a performance vehicle, you just need that extra step and look at things more carefully, BUT this engines are solid IMO and they love to be at WOT
Yeah, like these guys said, i'd look for a really good maintenance history. documented maintenance, 30,60K mile, etc services.
Honestly, if the maintenance looks good, just drive it a bit, let it cruise, and listen to it. make the salesman shut up, and just see if she's smooth. You'll be able to tell if it's been beaten on. at 100K... it'll come out