Today I played my first larger-scale game (as opposed to the starter set alone). The forces were Luke and Wedge against Vader, Dark Curse, and Academy Pilot.
The first game saw Luke take a bad turn and get the entire Imperial squadron's blasters on his tail. His shields dropped, but he continued. Wedge managed to capitalize on this, blinding Dark Curse and forcing the Imperials to evade. The ensuing melee saw both TIE Fighters destroyed (Luke one-shotting the Academy Pilot), leaving Luke and Wedge to take on Vader. Vader managed to outmaneuver both and finished off Luke. Wedge couldn't keep up with the dark lord, and was eventually shot down as well.
The second game was extremely similar, except that Luke and Wedge swept the TIEs away in the first few turns, effortlessly. This left the Rebels with a significant advantage over Vader. But Vader didn't care; he managed to catch Luke coming out of a Koiogran, and duelled Wedge very successfully after that.
What I took away from this? Vader rocks, straight up. I'd argue that he's a little undercosted, even considering how excellent Wedge is for the same points. X-Wings can and will kill a healthy TIE in one shot, and fairly often. Keeping TIEs alive seems to be about rolling out of the sights of X-Wings, but that's impossible to do with lower skill, and one of the reasons that Vader is so great -- he gets to choose his fights.