Well, as the regular starter the last 3 years the Redskins are 24-23-1 and while he hasn't led the league in yards or TD's, he's averaged well over 4,000 per season and accounted for 30+ TD's each of those seasons. He did lead the league in completion % at 69% which is pretty good, especially when it's attached to production in other areas.
But, last year is what sold me. He lost his OC McVay, lost his two best WR's, his TE got hurt and they had no running game but he still had a very good year. If he's going to put up 4,000+ and 30TD's on a losing team with few weapons, I think he's the real deal.