Emperor Gentle reminder to reboot after large updates. You end up with mismatches between what's on disk and what's in RAM. Generally not too much of a problem, but definitely gets worse if your running software is effective.
Believe it or not, Budgie and MATE also share a fair bit of code with GNOME (especially GTK) so you can expect to see improvements across the board for them and other GTK applications.
Edit: And the images in the Software Center were mainly just us needing to rebuild our AppStream data to match the new format.