I've been very impressed with their service. I even got an email from them 10 minutes after FedEx delivered the package saying that my tickets had been delivered. Someone posted a story on Rock's about getting a phone call from them saying that the seller pulled the tickets and they wanted to offer him something better.
I have a friend who's explored several Craigslist listings and he thought they were all scams. I explored one and it was definitely a scam.
Prices there seem to be rising but after studying this thing from a bunch of angles on various sites, I couldn't ignore the sense of peace of mind StubHub gives.