Umm Sean Cunningham SGI IRIX was better under XSGI - they fixed what was wrong with X11 while maintaining a minimal compatibility level. I'd call that impressive. Plus its a lot like AmigaOS all in all - but im not gonna debate its merits. Too tired
Under NeWS the Personal Iris 4D 35TG was perfectly usable in 1992. Simply "upgrading" it to the Motif based, non-Display Postscript GUI as well as additional bloat rendered these machines as doorstops (fuggetaboutit if you had a 4D25), using the
same application software. That OS required upgrading to Indigo Elan hardware, at the very least, to feel like you hadn't taken two steps backwards. Their baseline Indigo graphics didn't even work properly with that initial release of the new OS (4.x).
SGI was only able to remain relevant for a few more years after this as a workstation vendor with both Intel and, for a period, DEC on their heals, catching up on speed and kicking their ass on price. It was a sad state of affairs when folks had faster systems on their desks at home than what the company was still likely paying for sitting on desks at work.
Don't even get me started on their garbage toolkit that not only performed bad but looked bad no matter the hardware you were running it on. It should come as no surprise no major applications used it, they mostly went straight at GL. Not from Wavefront, Alias, SESI, TDI, Discrete, etc. Maybe ASDG but their interface was a slug and their I/O even slower and it was tolerated simply because their shape warping was the best implementation that's ever been and once morphing had ceased to be vogue their software was still the best roto tool available for SGI, even though it was slow, because the roto splines in everything else were just that bad.
Under the hood, yeah, IRIX was a solid OS. The GUI sucked since they dumped NeWS though, sorry. Maybe folks in academics never noticed. In CG/VFX animation, it wasn't a pretty time.