I went from 2004 right to 2014 in that year, and that jump alone was a breath of fresh air.
Right now, 2021 is installed and running:
Drawing History - Something I haven't had to use yet, but with the breakneck speed at which our clients change things, I can see it possibly saving me the trouble of keeping multiple versions of things.
Performance Enhancements - I'm heavy on the 3D side of things and using a 16 core processor, so taking advantage of multi-core is nice.
Purge Redesign - Getting used to it and it's decent.
There were a few hiccups in lisp routines and a plot file that needed an adjustment going from 2020 to 2021, but those were minor.
Pretty smooth sailing so far.