Jake did have a terrible year last season, but it wasn't all his fault. I think having a fresh start is exactly what Jake needs to bring back his game, he still has a good enough arm, there were times his arm looked stronger, which is something alse he had to adjust to besides his new QB coach on the Panthers that tried to change some of his QB'ing techniques.
After watching Jake since 2003 with the Panthers it has become apparent when he struggles. Like most QBs in the NFL, Jake struggles when he doesn't get good enough protection from his OL. The Panthers have never been good at pass protection while Jake was their QB, they're good at run blocking, but not good at pass blocking. Jake was hammered too many times while playing QB for the Panthers, but when they did manage to protect him somewhat and give him ample time, he excelled. When the Panther's OL failed to give him time to make his reads or even time to complete a slant pass, Jake struggled. This first came apparent in the NFCCG with the Panthers playing the Seahawks in 2005, Jake was rushed and hammered the whole game, the Panthers were down to their 3rd or 4th string RB leaving them with Steve Smith as their only offensive weapon. The Seahawks tripled covered Smith taking him out of the game and then pressured Jake and in return shut down the Panther offense. After this game opposing teams learned how to shut down Jake and the Panthers.
If the Brown's OL manages to protect Jake reasonably well and give him time, there's no doubt in my mind Jake will have a good season. Another thing that actually made things difficult for Jake was Steve Smith. Smith would pressure Jake to get him the ball and with opposing defenses keying on Smith (Smitty) this lead to many of Jake's interceptions. Jake's best season was the 2004 season when Smitty missed the season after the first game against GB with a broken leg. Also, in the 2008 season Jake won the first two games of the season when Smitty was out with a suspension, the Panthers lost the 3rd game when Smitty came back and played. The added pressure of getting Smitty the ball didn't help Jake's game. Now that he's a Brown, he won't have to worry about Smitty crying about not getting the ball thrown to him every time.