Not sure about "full time", but I certainly used it lots when at college many moons ago! This was at the time when educational computer rooms in the UK were still mostly full of BBC Masters and had the odd few Archimedes.
Unfortunately, the Archimedes were usually found running BBC BASIC programs or text-mode PC applications via the Acorn-supplied PC emulation software.
RISCOS did get some use though, via native applications such as Pro-Artisan (graphics) and Impression (DTP).
I still have a couple of Archimedes, but they don't get used much! There are a couple of emulators available for Windows if you're feeling nostalgic!
- Ali