After playing some two weeks now, I can say I miss a couple features, excluding the missing enemies, slopes and checkpoints;
- the ability to zoom out in builder mode and see a complete overview
- see the subworld in the list entry beside the main world (you only see the main world now) so I can also see where most deaths are in there
- a prompt to give a Star or reaction or not when skipping a level in the Mario Challenge
- the ability to place a sign to give hints or explanations to players
- the ability to slightly update a level once uploaded under it's own ID, keeping it's stats, like by giving the builder the chance of changing up to 10 blocks or something