Today my BoS SSJ4 Goku arrived.
Pretty happy with the overall quality, colors are intense and the lack of any shading makes it look like a mini version of the SMSP Anime SSJ4 Goku. I actually thought it was just the same sculpt with only the expression changed but putting both of them together shows multiple small differences between the two. The metallic hair gimmick of the BoS line translated well into black hair even if is somewhat subtle, you need to see it from specific angles to see a blueish, metallic shine on the hair, otherwise, it looks jet black. However, it looks pretty distinctive when placed alongside the other SSJ4 Goku's figures with the matte hair.
My big complaint is the decision to use a big round base instead of the small "weight" used on previous BoS figures or the SMSP's one since those make displaying them easier. Luckily it can stand perfectly on his own so is a pretty minor issue.
Some more pics