The only thing I read about is some changes in the animation tools that was a deal breaker for some users. I can't remember the specifics since I don't do animation.

You can always carry on using V4 in DS4 but Genesis itself doesn't need as much 'investment' as previous new figures. Out of the box, V4 textures work, V4 wardrobe works, that's a huge saving immediately.

If you've got a specific V4 character that you want to carry on using, you may need to buy the convertor to get V4 Characters to transfer to Genesis. The various convertors allow you to keep using all your existing runtime but with Genesis' capabilities. ( I think the only exception is V3 textures because of the complexity of combining the seperate head and body texture maps.)

Even without Genesis I think the improvements to DS4 make it worth the pain of transition. ;-}

regards
prixat