Don't think Smith was drafted in any worse of a situation then the typical #1 pick. Yeah, 49ers weren't very talented in his early years there, but neither were the Colts last year. He's probably an average to slightly above average QB. If KC has a great offensive line, then he'll probably be fine. Not going to lose games for KC but probably doesn't win many. Perhaps a suped up version of Kyle Orton.
Going to be on KC's defense to keep them in games. And I'm in the camp that they are at best average defensively. They don't get a lot of sacks, force a lot of turnovers and for as often as they are on the field, would think they wouldn't be last in the league in tackles. They have some talented players, but there are a lot of holes on their defense. Talented teams will have little trouble finding them.