While I do question his off field activities, Manziel can play and is a winner on the field. I wouldn't trust the guy with the family dog but I'd certainly put my trust in him to win football games. I'm sure there are plenty that will question my judgement, but to those who do, I'll bring up one name. Tim Tebow.
Yes, Saint Tebow could do no wrong off the field and was a proven winner. But he wasn't a conventional quarterback and couldn't throw, yet he parlayed his on field faults into being selected in the first round by the Denver Broncos. He eventually was named the starting quarterback and led the Broncos to a playoff win over the Pittsburgh Steelers. In my opinion if a team can put trust in Tebow, who was a flawed product, then skeptics shouldn't pick on Manziel so much.
While it's true that he's a hard driving individual off the field, there is no doubt about his abilities on the field. I believe Manziel can succeed if he's put in the right team environment. Right now Manziel is more sizzle than steak and if he can't be reined in off the field then he'll have a short career.