I've had the sluggish rotations as well. Sometimes it gets stuck and i have to reboot. Just the usual beta niggles.
The new wigdets layout and design could probably do with some refinement as it looks pretty odd, especially across two columns.
Split view safari and 3-column Notes are OK but I'd typically use Safari+Chrome and OneNote so they aren't major benefits to me.
TBH it's fairly sparse in changes although there is time for that to change.... and I'd really appreciate a better split view task selector than the current massive long list.