Per MLBTR. Gomez' primary qualification appears to have been a 5.96 ERA last year and miniscule K rates in the majors. Well, that and he played for Cleveland. On the other hand, he hasn't quite turned 25, although he's spent significant parts of three seasons in the majors. He throws in the low 90s and, according to Baseball America, lacks an out pitch, which is reflected by low K rates in the minors as well. He'll have to go on the 40-man roster.
UPDATE by Charlie: Latimore has significant power, but strikes out too much and doesn't get on base. A number of the Pirates' outfield prospects have lapped him in the past few years.
You may remember Gomez from this game, in which Pedro Alvarez hit two homers against the Indians. As WTM suggests, there isn't much to recommend him, although he's still relatively young and he does get ground balls. The Pirates are a much better defensive team than the Indians were last year, and Gomez isn't likely to allow 15 homers in 90 innings, as he did last year, while pitching in PNC Park. But that's reaching. Luckily, the Pirates didn't give up much. This move may reflect the Pirates' need to acquire more depth in the rotation now that the Francisco Liriano deal is in limbo and Rick VandenHurk has departed for Korea, but unless Gomez dramatically improves, the Pirates would have to be in pretty big trouble to consider starting him.
Gomez is also out of options, so it wouldn't be a surprise to see the Pirates try to sneak him through waivers at some point, as they did (unsuccessfully) with Chad Beck.