The Cubs have a vacancy at 2B. Jeff Baker is a nice player for a team that sucks, and Barney's future is as a top bench player. Kelly Johnson is one of the best bats available in FA next year, and he happens to play 2B.
Johnson last year broke out with a .284/.370/.496 line in Arizona, a hitter friendly park. He's also put up lines like .287/.349/.446 ('08) and .276/.375/.457 ('07) for the Braves, so there's no questions about his bat. He's not a great defender at 2B, but he had a strong season last year and he might have been affected by the Braves trying to play him in LF at one point.
Personally, I root for DJ LeMahieu to find his power by 24-25 and take over the 2B spot. That said, Johnson offers a strong all around game immediately (well...for 2012+), and is behind the big 1B bats for best FA position player available. I've actually followed Johnson as one of my sleeper players since he was a Brave, and wouldn't really consider it a bad move for the right price. He's a secondary option though, and in that sense I'm sure there'll be plenty to complain about. For instance, if they make a former D'Brack of a current D'Back it better be Upton.