Having an OS which boots from hardware is always a feature to me - no matter how badly you screw up your system, you just do a hard reset (boot holding R) and get a working OS and GUI. You can still patch it by defining a boot app, but the core system is always there, safe from mishap and malware.

And yes, the OS was starting to show its age (both graphically and with its cooperative multitasking) by the time Acorn was broken up, but at its peak it was miles ahead of the competition, and was definitely an under-appreciated pearl.