I'm not a huge Casey McGehee fan, and I love Veras' stuff - I'm pretty sure that if I were a Brewers fan, I would love this trade. (The Brewers no longer needed McGehee after signing Aramis Ramirez to start at third.) But I can see why the Pirates did it - I've been screaming as loud as anyone that the Bucs need an alternative to Pedro Alvarez, and McGehee, who at least was an above-average hitter in 2009 and 2010, provides one. (He was also hitting reasonably well in April of 2011, then hit really poorly for a couple months after spraining his thumb - I'm not sure if that means anything.) If, as we all hope, Alvarez doesn't completely crater, McGehee can be a useful bench player - in addition to third base, he can fake it at second and first as well.
The Pirates also have a bit of a logjam in their bullpen. I don't think they should have considered non-tendering Veras, whose breaking ball is a thing of beauty, but the fact that it was even a possibility suggests that they have enough in their 'pen to get by without him. Meanwhile, McGehee, who's entering his first year of arbitration, should be pretty cheap. I don't love this deal, but I certainly understand it.
It looks like Chris Resop, at least, can breathe a bit easier now, as this move appears to make it more likely he'll be tendered a contract.
UPDATE: Rob Biertempfel:
#Pirates GM says McGehee "gives us protection for Pedro and Garrett or can be starting option at 1b or 3b if one of them struggles"
It sounds like Jones will be tendered, and it sounds like the Pirates are beginning to settle on him as their starting first baseman.