It's really hard for me to say. I have been using 9.2 since the first RC. As a result I really am blurred as to what changed
IMO the improvements really seem to be GUI. Kernel remains essentially the same, and as far as I can tell nothing really undergoes a major revision other than OpenOffice 1.1. A lot of tools in the Control Center have been revamped, which is good.
Personally I always upgrade as it is easy and free

My upgrade has always gone smoothly.
Jkrohn