Hill spent three years as a backup in Minnesota under offensive coordinator Scott Linehan, who now holds the same position in Detroit. They have a comfort level that will accelerate Hill's adjustment to a new team.
Hill is the quintessential backup quarterback from this sense: He has proved he can come off the bench and win games over an extended period of time. He went 10-6 as a part-time starter for the 49ers over the past three seasons. Notably, the 49ers were 10-22 in the games he didn't start over that span.
He is good enough that he could push starter Matthew Stafford if the franchise quarterback falls into an extended slump, but not to the extent where he would challenge for the starting job in training camp.
The deal would end Daunte Culpepper's candidacy to return as a backup, a situation that probably wouldn't have been healthy for him or the Lions. Culpepper wants to sign with a team that will give him a chance to play over the long term, which is not something the Lions could offer.
A seventh-round draft pick in 2011, the 49ers' reported asking price, is more than a fair price for those attributes.