And it's not even that big of a deal, anyways. Neither Carr nor Hill is going to make much of a difference on this team. But for what it's worth, Carr has good physical tools and is a solid presence in the locker room. The Niners needed a veteran QB with the arm strength to get the ball downfield to Crabtree/Davis/Morgan, and who can potentially challenge Alex Smith for some playing time.
It's not that David Carr is any good; it's more that Alex Smith and Shaun Hill (and the free-agent QB class this year) are so mediocre. As long as the money was reasonable, I'm okay with Carr over Hill. Either way, this team will be hard-pressed to make the playoffs. What they need on offense is a big-time Pro-Bowl-level upgrade (either o-line or QB), not exchanging one backup for another.