SideShow has really done a great job on this one. I'm THRILLED with Vader!
Here's a quick rundown of the things that jumped out to me last night:
The arms ARE skinny (especially the forearms). But the gauntlets are flared, so it really helps to conceal how thin they are.
The body that was used is very nice, although I hate how these Prometheus bodies (and variants, apparently) have a really hard time in the crotch area. I noticed it on my Boba Fett and Snowtrooper, as well (there's an ugly 'gap' that looks unrealistic). Although I'm sure most won't notice/care.
I don't care for the way that the gauntlets were made. Although they keep them all one piece, I do prefer the method that Medicom used (seperate gloves/gauntlets), as it allows for tremendous amounts of posing.
As for the size, I feel that since the figure is so well-proportioned, the height makes no difference. He looks/feels totally scale.
The helmet itself is a MASTERPIECE! SideShow has done SUCH a good job with the sculpting and paint application. The helmet appears to be symetrical, but it looks beautiful in every way.
The cape and tunic drape perfectly, giving them the appearance of weight. I love the collar (although I wish they could have done the same with the lower cuff).
The jumpsuit does bunch up at the crotch, but the pattern of the 'fabric' is outstanding. It really looks like a scaled leather suit.
The included helmet stand, to me, is worthless. The reveal helmet is outstanding, and the inner details look spectacular, but I won't use it for anything.
The large light-up stand, to me, is worthless, and it's HUGE. I would rather have had a non-light up stand like Luke's (or even a standard SideShow stand).
The Anakin head sculpt is nice to have, but it won't ever, ever be displayed on my figure. The paint application on it is solid, but still light years away from Hot Toys quality.
The Exlcusive is neat, but worthless. No one will ever use it.
I haven't used any of the electronic features, and I probable won't.
That's just a quick summary of my first impressions. The negatives that I've listed wouldn't be negatives if the figure wasn't so expensive.
Overall, it's safe to say that this is the finest figure SideShow has ever released, and it'll probably be the standard-bearer for quite some time!