Finished the main V2 build and absolutely loved it. Here are kind of my initial quick impressions.
On the negative side, by far the biggest issue has already been mentioned here. The arms do not hold together well under posing. I don't know what it is, but they tend to fall apart if I'm not careful posing. This can happen at any of the connections. The elbows can come undone, the part that connects the shoulder to the bicep can loosen and fall out and the shoulder itself can pop out of the main body. If i'm slow and careful, it's fine and it's not something that's hard to put back together. It also holds perfectly well in a static pose once you get there, so I guess it's really a minor annoyance than anything.
You also have the proportions. The chest looks really wide in photos, but in person I'm having no issue with it. The two biggest changes for me is that the shoulder armor feels too small and the neck a hair bit short. I suspect the former was to allow room for the AB pieces later on and the later was due to the transformation clearance.
The lack of a waste joint has been mentioned here, but I honestly don't see how that is fixable with the current tech and the transformation. The way it clips doesn't allow for a waste swivel, but it does mean the figure is extremely solid in MS form and that will likely help a ton when you stack all the AB weight later on.
And that brings me to the positive, he's so damn solid in MS form. You wouldn't know he was a transformable MS. Bandai has done a great job ensuring every section clips into every other at multiple points and you can feel that. I'm glad because the AB parts are really going to need the solid base to clip on. Also, the transformation isn't nearly as finicky as I imagined. Everything feels like it transforms in probably the simplest way it can while still allowing all the detail. The top and bottom fighters feel really flimsy on their own, but when you add a core bit they sure right up. I doubt I'll transform them more than a couple more times, but I'm impressed with what bandai accomplished.
Most of all, this kit really embodies the V2 and that's what makes me excited. It feels super powerful, yet sleek and fast. This colors look really nice as well and I particularly dig the effect on the beam shield. This feels like Bandai's best attempt at a MG transformable MS yet. It's not perfect, but it's close enough.
On the side, I have kind of no idea how the backpack parts on the AB upgrade will work. The core fighter's transformation mechanism takes up almost all the chest space. Unless they do something really clever with parts I'm not seeing, I suspect we'll need whole new core fighter or maybe even a non-transformable core block (though that seems too off model for bandai). I could see them replacing the booster parts with ones that have slots to click the backpack in, but that would eliminate booster posing and I hope they don't go that direction. I'm eager to see what solution they come up with. If the base V2 is anything to go by, there won't be much to worry about. Given how good the V2 looks plain, that kit is going to be a damn sight with the AB parts and wing effects.