I was neutral (at best) on Bevell after 2011.
He's won me over this season. His ability to consistently construct long drives this season is the best we've seen since Mike Holmgren in 2005. I think his playcalling shines the most when Carroll/Cable allow him to call more passing plays.
He's also brought some nice trick plays to this offense (Rice/Tate throwing the football, etc. Those plays have almost always been successful too).
He's also introduced Mike Rob as a surprise 3rd and short back and it's worked very well.
Throughout the season, he's been flexible and changed the offense to adapt for Wilson's needs.
I also feel like it's probably not a coincidence that so many players on offense have developed significantly since Bevell came here. Even the good players he inherited (Rice, etc) have looked very natural in his offense. Which makes plenty of sense in Rice's case given that Bevell's offense is the only NFL offense he's ever played in.
The only time his playcalling leaves something to be desired is when the team goes run-run-pass-punt, or when the team was throwing 4 or 5 backwards lateral bubble screens a game. Those were stupid- but then again, the team realized those things weren't working great and moved on from them.
This is just the 2nd time that Bevell has had a quality QB running his offense, and unsurprisingly both of those offenses were very efficient and won a lot of games.
I would hope that Bevell returns in 2013, but if he goes to Wisconsin I'd wish him well and hope that Seattle could pick up a home run addition at OC.