A lefty finesse-type pitcher, Maholm has spent his career with bad teams, mostly the Pirates, which is a tough situation for this kind of pitcher. With a better team, he may improve; he was already having one of his best years (only mediocre) with the Cubs.
The Pirates made Maholm the eighth overall pick in the generally weak 2003 draft; he put up a 3.10 career minor league ERA, but without the peripherals you would expect from a high draft pick. He was called up to the majors, and put up a 2.18 ERA, going 3-1. He hasn’t approached that again, and probably won’t except for short stretches. For his career he is 62-79 with a 4.30 ERA. He’s a better pitcher than that, but not that much better.
As stated above, finesse lefties like Maholm can have particular trouble when playing on a bad team. With a good offense and a good infield defense, they can thrive, and even put up results better than their real ability. The Braves have the offense, but not the defense, except maybe at shortstop. He could have some ugly games; he could also have some really good ones. Most importantly, he gives the Braves a reliable back-of-the-rotation starter to solidify a shaky rotation.