Overall I like the general feel of the new UI. It is a lot cleaner than the previous version.
The floating dialogue box for posting new posts is a lot better than what we had in the previous UI. The curved appearance of threads is a lot better.
So here are some issues I have that I hope can be improved upon:
The placement of notifications, messages and saved is odd. In fact, the choice to put the link to your profile page on the bottom left also makes little sense. The profile image and profile page link should be on the top left. It would make more logical sense to move notifications, messages and saved directly under the home and explore icons.
Combining settings into the menu from the profile image icon, makes no sense at all. This should be taken out of this selection and placed underneath the notifications area (which I already suggested you move to the top left.
The options on the left side are too flat and need to be tweaked to pop out from the overall design. Way too flat.
Also, the trending topics seem to be missing in this new design. I would request that you add this feature into the new UI.
Everything seems to be very squashed and many of us would like a feature to adjust the column width, or at least make the post feed area wider. Or what might be a better idea, create more separation between the three main columns, its very squashed.
Finally, where is the mastodon logo? This little thing in the “powered by mastodon” is hardly noticeable. Restore a more prominent logo.