Polenzani has come up through the ranks at the Met, doing well with the "important secondary" parts and now being given the leading roles like this one. (He's also paired with Netrebko in a Don Pasquale that's out on DVD.) I've seen him in recital and he's superb in that context too.
Netrebko is definitely a big star. In addition to the quality of the voice, she's one of those people with a certain magnetism that makes her interesting to watch.