In terms of functionality, 8.1 isn't bad but I can't stand the flat square theme that could've dropped straight out of the DOS era. It's so ugly.

I understand why Aero didn't continue on in its Vista/7 form, but Metro swung way too far in the other direction. The Fluent look used by Windows 11 is a nice middleground that I wish 8, 8.1, and 10 could've adopted instead. Too bad the rest of 11 sucks.