You can track Pirate prospect progress in the Arizona Fall League here. Neil Walker has had two hits, including a homer, and two walks in his first six plate appearances. Adam Boeve has hit well, too. Of course, one reason they're hitting so well is that teams don't send healthy, high-quality pitching prospects to the AFL anymore - they often send guys like the ones the Pirates sent, Matt Peterson and non-prospect Shane Youman. Actual pitching prospect Bryan Bullington is supposed to be on the team as well, but he hasn't played yet; neither has first baseman Brad Eldred.
At the same site, Baseball America has compiled all-star teams for each minor league level. Zach Duke is there at Class AAA, Jose Bautista is at AA, and Walker is on the team for Low Class A. Before you get too excited about Bautista, though, note that BA named Justin Huber, who was passed from the Mets to the Royals in exchange for the right to trade Bautista to the Pirates, the top first baseman anywhere in the minors.