that alone? no. but you throw in his average, and to top that off his injuries returning punts (i know he reinjured his knee in 08 because of it, and he may have in 07?) and his recent breakout performance on offense, its best just to keep him on offense where his best contributions lay. We don't need him on special teams, where he's had ball security problems, injuries, and bad averages.
We can throw someone far less important on punt returns, stress to them ball security, who will get roughly the same average in yards per attempt. The only thin we'll be sacrificing by doing so is 1 TD per year roughly that Bush gave on average.
and considering we have the number 1 offense in the NFL, That sounds like a solid deal.