Buchholz, who is in no way related to Clay, broke into the league as a starter with the Rockies before putting up a very impressive campaign as a reliever in 2008, sporting a 2.17 ERA with 56 strikeouts and just 18 walks. He missed all of 2009 after Tommy John Surgery, though, and was less impressive in his return, struggling in 21 minor league outings before putting up a 3.75 ERA in limited innings split between the Rockies and the Blue Jays.
This seems like a great move for the Red Sox. While Buchholz is arbitration eligible and thus not as cheap as some other options might have been (still, only $1 million or so), he was impressive before his Tommy John Surgery, and has only had a very short time to recover from it. If an offseason of throwing and conditioning can return his arm close to his previous form, he could be a very valuable asset indeed.