The draft isn't over yet, and I still have much to learn from opinions of people more expert than myself, but here are some preliminary thoughts.
The Bucs took college players in the first five rounds. The first two of them, Vanderbilt third baseman Pedro Alvarez and Fresno State righty Tanner Scheppers, are so unlike the typical Dave Littlefield draftees that I feel like they must be good. Alvarez is a top talent and a Scott Boras client who the Bucs will pay real money to sign, and Scheppers is an excellent gamble for a team like the Pirates with the 40th overall pick. He was once regarded as a possible top ten pick, but then he underwent a stress fracture in his shoulder. That's an unusual injury for a pitcher, so it's too early to see how quick and complete his recovery will be. The bigger problem may be that there's some other issue we don't know about that caused the fracture. But, if healthy, he's a potential impact talent with great stuff. The Mariners' doctors thought Scheppers would be fine and gave the team their blessing to take him with the 20th pick. We'll see; there's a lot about this pick I don't know much about, but it looks to me like exactly the sort of high-upside gamble the Pirates should be taking.
In the third round, the Bucs took Oklahoma State shortstop Jordy Mercer, marking the second time in three years the Pirates took an Oklahoma State middle infielder in the third round (Shelby Ford played there too.) They took Pepperdine shortstop Chase D'Arnaud in the fourth round. Both seem, from what I've read so far, to be unspectacular but legitimate picks, and they should fortify the middle infield positions in the Pirates' system--you can never have enough middle infield prospects.
With their next pick, the Bucs grabbed lefty Justin Wilson, also from Fresno State. It's interesting, as Vlad noted in the comments, that three of these first five picks were from California; California is a major talent hotbed, and the only reasonably important Littlefield pick I can remember from there was Jared Hughes. The Bucs just had no presence there. Apparently that's changed, at least enough for the Pirates to send someone to a couple Fresno State games. Anyway, judging from his scouting video, Wilson has good velocity for a lefty (he topped out at 91 and generally kept his fastball in the high 80s), although it looks like control may be an issue.
In the sixth round, the Bucs took Texas high school outfielder Robert Grossman. Grossman isn't known as a toolsy player, but he plays hard and has line drive power and decent speed. He may overachieve.
Based on what I know right now, this looks like a good draft so far. I think the first two picks are terrific, and the last four are interesting for different reasons.