Still have to go with Rondo. Sully is nice...but what's really his upside, another Carlos Boozer? That's a very nice player, but as the Bulls will tell you, not a centerpiece of a championship team.
While Rondo has his flaws, there have been times when he's been on the same court as LeBron James and (at least for one game or one quarter) has been the best player on the court. In a league where dominant superstars always seem to prevail, I'd hesitate very strongly before giving up the closest semblance we have to one.