Agent was by far my favorite. There are only three weaknesses I can think of:
Otherwise, the Sith Warrior had some excellent character moments and very distinct Light vs. Dark progressions; apart from that one extremely poorly handled Incident I thought it was very good. Jedi Knight was solid and traditional, and that's not a bad thing. Smuggler and Trooper both had great Act 1s with personal grudges to pursue; both weakened after that. The Consular had a distinctive feel with all the guests on board; it didn't really grab me but I appreciated the change of pace. The Agent was just awesome.