As I recall, the main issue with the earliest versions of OS X is that they were slow, somewhat unstable, and would occasionally do really weird things (like how on my summer 2000 iMac DV, OS X 10.0.x once randomly decided it wasn’t going to draw the cursor any more and had to be reinstalled before it was fixed). This led me to spend a fair amount of time booted into OS 9 with an Aqua Kaleidoscope scheme applied and SmoothType installed for that luxe OS X style text rendering.

10.1 made things a little more stable but wasn’t revolutionary.

10.2 Jaguar on the other hand… holy cow. It was so much faster and more stable on my iMac it was absurd. The speed gap was still there but nowhere near as dramatic, making it a lot more usable. This is where I went almost full time booted OS X outside of the odd random thing that didn’t play nice with Classic.