We had the pleasure of seeing the Sunday matinee performance with Herrerra/Hallberg and a last-minute surprise substitution of Carreno as Ali (instead of Saveliev). All in all, it was a very enjoyable experience. The endless parade of show-stopping numbers in the first two acts was memorable and truly exciting to see. (and a young corps member we know explained to us afterwards that the unreal series of flying, leaping turns that Herman Cornejo does in Act I is called a "540": It can't really be described, but suffice it to say, seeing it is one of the few honestly jaw-dropping moments I have ever experienced in watching a live performance.)
I don't know who has prettier feet: Herrerra or Hallberg

but I do have to say that I felt like Hallberg suffered a bit in comparison to Carreno. to be sure, Hallberg's extension and lines are simply exquisite, some of the absolute loveliest I have ever seen in a danseur. But Carreno has the ability to occupy a stage like few performers do. He's just a much more complete performer than Hallberg is right now.
Quibbles: the third act. What the...? I have never seen Le Corsaire all the way through. OK, once you get past the silly storyline, it's quite possible to relax and just enjoy, but that third act was just about unnecessary. And the gratuitious use of children? I'm sorry, but I didn't come there to see wobbly kids en pointe. I realize it probably helps sell tickets to cast these local children but that whole Pasha's Dream sequence was amateurish at best. Even with a muted Herrerra and Reyes and the ABT corps weaving in and out, it still was close to painful to watch. Why, why, why?