Aside from new v4 features, how about some of the features in v3 that still have issues? Convert Scene-mostly useless, Motion Blur+Mograph=Crazy Results, Team Render slowdowns, some Multi-Pass issues-still can't get anything out of Velocity Pass. Those are buttons/features that were released in the final v3 that didn't fully work. I understand thing like render instance problems need to be worked out with it being much more complex, I'd really like to see those items ironed out before adding more features.
Not having full use of Mograph's power is a big deal to motion graphics people. Don't mean to whine, just want everything working.