I finally picked up Vader last night, for some reason he's been hardest to find for me since that first time I saw him and was low on funds so chose Obi-Wan over him. I wanted to get Vader now before the X-wing revision case started hitting as the rev1 case has no Vader (the wave 1.5 case does though, but who knows which will show up more often).
I cracked out my old Action Fleet Vader's TIE Fighter, the original version before they realized it was over-scale and redid it about 20% smaller, and compared it to TF Vader's TIE. The AF and TF versions are with millimeters of each other in terms of overall size, they're that close, but it's blatantly clear which one is which at first glance as the AF version has much better and more accurate detail - I accept that TF Vader had to take liberties with the design, and it's not too far off from the overall concept.
Against Obi-Wan's TF Jedi Starfighter, I'd say TF Vader makes a really good foe, Vader's slightly taller in bot mode which is good, and I don't think his head is up too high as much as folks have been making out, it's only looks about half a cm too high off the shoulders and that's in part due to the neck design. Vader's saber blade is slightly longer than Obi-Wan's, which is how it was in the movies.
I think the designers made a fun toy out of Vader, but they dropped the ball with the wing/cape design, they were on the right track but the other wing should have connected to the cape wing so it could have lengthened the cape, there's even a hole which could have that but it's slightly too small. Oh, and they really should have made the Vader pilot minifig lock into the cockpit in bot mode, it just rattles around in there because the chair in there is too shallow.