Well first you can not have to upgrade to 512MB ram, kinetic+, viewfinder++, usb card+, gigabit network card, ide card++, that's got to save you about 500-700ukps
Then you can play video much better if you have cineroma. And sample audio better it would seem.
Then everything that's annoying because it's too slow on your RiscPC should be fixed. So you can again work with the high res complex DTP documents you want to, or realistically encode mp3s perhaps, or handle 100MBs of data. And run emulators faster.
The only thing I can think of becoming much more usable is video editting.
What can you do on a 2GHz PC compared to a 1GHz or less? Play more games and watch higher res video.