Okay, assuming we have everything now:
-P- They sent RP Javier Lopez to the Giants. They got SP Joe Martinez and OF John Bowker.
-P- They sent RP Octavio Dotel and $500,000 to the Diamondbacks. They got SP James McDonald and OF Andrew Lambo.
I've said over and over that I would prefer the Pirates trade for Class A-type talents if it means they can get more upside. That said, I'm not sure there's much to quibble about here on those grounds. The Pirates really didn't give up a whole lot - Dotel and Carrasco were relatively valuable relievers, but they're still just relievers. So it shouldn't have been expected that they get much.
The players the Pirates got are mostly help-now types, but McDonald, in particular, used to be a very well-regarded prospect, and his performance actually hasn't faded all that much since that was the case. His upside is probably something like a #3 starter, which isn't usually the sort of thing you can say about a 25-year-old Class AAA pitcher.
Martinez and Bowker are lower-grade talents, but both have a chance to be helpful, and the Pirates only dealt Javier Lopez to get them. Bowker has struggled in limited opportunities at the major league level, but he has mashed at Class AAA, so he should probably get another shot. It's unclear, though, how the Pirates plan to give him one - they already have four pretty good starters at first base and the outfield in the majors, and with the addition of Snyder, Ryan Doumit is going to be vying for playing time at those positions, too.
I really like the addition of Snyder, who should provide the Pirates with a good temp at catcher until Tony Sanchez is ready or something else happens. He's arguably as good a hitter as Ryan Doumit is, with much better defense, although he does struggle to control runners. In any case, the Bucs did well to get Doumit out from behind the plate, and at a very low cost in terms of talent.
Lambo is the wild card here. Like McDonald, he was once among the Dodgers' top prospects, but unlike McDonald, he probably won't be with the Pirates anytime soon. He'll probably be at Class AA, where he's been for the past two seasons. He's struggled to master the level, but then he hasn't been overwhelmed either, despite skipping Class A+ and being somewhat young for the league. It would be hard for me to argue that a couple of random Class A arms, which is about the return I would have expected for Dotel, have more upside than Lambo does. He isn't a surefire prospect by any stretch, but he's a nice addition.
The Pirates continue to add prospects other teams have soured on. That strategy hasn't worked brilliantly yet, but it helps to remember that in this case, the Pirates just aren't giving up a whole lot.
With the departures of three relievers, I'd look for Joel Hanrahan or Evan Meek to take over the closer's role. McDonald and Martinez will probably join the team immediately, perhaps with one of them stepping into Daniel McCutchen's rotation spot. Snyder obviously will join the team, too, probably sending Jason Jaramillo back to Indianapolis. I'm not sure what will happen to Bowker.
UPDATE: McDonald will join the Pirates; Bowker and Martinez will go to Indianapolis; and Lambo will go to Altoona.