Pair got shipped to my work so I wasn't able to open it until I got home. The primeknit on these are definitely more sturdy and not soft and loose like the OG350. You can really feel the extra padding on this shoe. The boost is definitely more soft than the OG350 and there's more bounce to the V2 than OG350. The color is also a lot darker than I expected.
As far as sizing, I went a full size up from my OG350.
My true to size is 8 (sometimes 8.5)
OG350 I had to drop down to a size 7.
UltraBoost I wear a size 8 and they fit snug which I like. (OG UB size 8 feels more snug than my Continental (MG, Cream) size
Flyknit Racer I wear a size 8 and they fit perfect - not snug, not loose.
I went my UB size for the V2 and the initial wear surprised me. If you went true to size then it will be snug - which I like. I have narrow feet so the snugness feels good though. You can really feel how snug it is around your toe area. If you're the type that likes having some room up there, then go up .5 from your TTS. Not sure what to tell you if you have fat and wide feet though.
I gotta say, I still prefer the OG350 aesthethics over the V2 aesthetics - the stripe is growing on me. But as far as comfort, the V2 feels better than the OG350 from my initial wear.