Nene is foul prone, and as you said, they lose frontcourt depth for a PG who isn't a franchise PG and a SF who is no better than the one they had already. I personally would never trade an "elite" center for a marginal PG unless you're in a situation where you're trying to clear cap space or getting rid of a team cancer in the process. If that's what Denver is trying to do, then it's a good deal for both teams.