Bleacher Report is going through their annual Top 1000, and Matt Miller ranked the Tampa Bay Buccaneers center Evan Smith as the number 16 center in the NFL.
Dietrich-Smith is an example that a great quarterback can make an offensive lineman look really good in the passing game, and a bad quarterback can have the opposite effect.
That's about where I'd rank Smith, too. He wasn't exactly good last yer, but he was put in a pretty terrible situation and has a history of being a much better player.