Trade's official:
Pirates get Jerry Sands, Stormy Pimentel, Mark Melancon, and Ivan de Jesus
Red Sox get Joel Hanrahan and Brock Holt
Brock Holt makes it a bit interesting, but he's basically a slap hitter with bad defense. De Jesus is a former top prospect (surprise!), and looks to have been very successful until he broke his leg a few years ago. It looks like he can take a walk, so he's probably a better utility infielder than Holt. Melancon could really be a key in this deal--he's capable of giving an equivalent performance to Hanrahan, which effectively makes the deal a wash plus a gamble on Sands/Pimental.
Edit: after reading up a bit, De Jesus looks pretty comparable to Holt--defense isn't good enough to play SS, and hitting (especially for power) isn't really good enough to be a regular anywhere else (also, 2B and 3B are pretty blocked). Counting that aspect of the deal as a wash, it looks like 3-for-1, and so a lot of the MLB value rides on Melancon. Apparently he had problems with Valentine, and the consensus amongst the talking heads is that he'll return to 2011 form in 2013. I'm fine with that, but fairly mediocre over all. Pimentel looks like a depth move, and Sands just adds to the logjam of corner OF possibles. Rosenthal is saying that you can look at this as a 5 or 6 for 2 deal, factoring in Liriano's salary and possible another bargain FA-type, but that's not really a fair way to evaluate a trade. I'd certainly opt to spread the money that way, rather than give it to a closer when there are multiple other options, but this is definitely not a cashing-in trade.
I don't really love the deal, and would put myself firmly in the "should have traded him a two years ago but obviously couldn't" camp, but I'm fine with this.