I'm pretty much echoing the majority of people here when I say this figure is very impressive and the feeling of the build quality and weight is awesome.
The proportions appear to be more accurate in my opinion. The overall look of the figure is just beautiful from paint down to details.
Something I've always been very nitpicky about is the accuracy of the helmet. It seems that Hot Toys has finally got a very accurate helmet done. The light up is also just amazing on this figure. The way they approached the lenses this time around is fantastic. The light shines through evenly and very bright and clear. Previously the lenses were just the clear plastic with the light coming through them, but I think the white inserts behind the lenses really add to the light up and the look of the eyes when the lights are off. I hope they continue this trend with future releases for the helmets as it looks so good.
I also hope the regular MMS armors can match the quality of the Die Cast series. If they were to revisit the old armors in Die Cast, I would go for a Mark I, II, III and VI.