Not a terrible deal, but highly dependent on whether the Braves' scouts have correctly pegged Sosa as a quality reliever. Losing Nick Green isn't a huge loss, other than the fact that he was local and provoked Boy Band reactions from young female fans. (The team needed someone to fill that role after Javy Lopez left. Now? I hope that Ryan Langerhans is a looker.) Green was hot when he first came up, but then cooled off and regressed back to his numbers from the minors. The Braves are trading him at his likely highest value, as they did with Charles Thomas.
Sosa's stats with Tampa were pretty weak, but remember, he was playing for Tampa. He struck out a lot of batters last year, but gave up a ton of homers and walks. In other words, he sounds like someone who would benefit greatly from Mazzone coaching him on taking a little off the fastball so he can locate it better. The Braves took a similar risk in acquiring Juan Cruz last year and he turned out to be one the Braves' better relievers by the second half of the year.
The #1 benefit from the deal is that every time Sosa comes in, I can go into "Scarface" mode and imitate Robert Loggia imitating a Cuban-American drug/car dealer: "You thought Omar was a stoolie because SOSA said so?" or "Let me tell you something about that greaseball c***-sucker. He is a snake. You turn your back on him and he'll stick it in." Everyone who watches or attends a Braves game with me should be on notice, although if they put up with the standing ovations for every appearance by Antonio Alfonseca, then they can put up with anything.
Atlanta still lacks a decent lefty reliever in a division where their chief rivals (Philly and Florida) both have lefty first basemen with prodigious power, but that's a relatively minor role to fill. It's more important to find quality relievers who can throw 70 good innings than lefty specialists who come on to get one batter.