I used it as my main desktop system for three years while working on a self-driving vehicle, in 2003-2005. There were versions of Firefox, Thunderbird, and Open Office, so you had all the essentials.

It's OK, but would feel dated to most users. The really great feature is that there is no lag. The consistency of QNX is impressive. This is a real-time system, not a warmed-over time sharing system. No swapping or paging. Proper CPU scheduling. So little "why did it do that?"

It was amazing to be able to restart the GUI without even impacting the apps that were running.

You must have been throwing a lot of CPU power at it, or perhaps I've just been extremely unlucky:

I've used multiple QNX based user interfaces and the one thing they all had in common was their lagginess and unresponsiveness.

What version did you try? When I tried QNX 4.24 on my desktop computer, I think it might've been on a 125 mhz pentium? Or a 486. The Photon GUI was snappy.

6.71, on a Pentium III.

>... No swapping or paging. ...

That's more of a function of your hardware resources and workload than the OS architecture you're running. E.g. a lightweight Linux desktop installed on present-day hardware will literally run with zero swap use - in fact, it will cache most disk access. (Unless you open something that hogs RAM, of course.) That may not be literally a soft-RT system, but from the user's POV it's just as snappy as one.

Tesla is using Linux and Qt UI which seems to work pretty well.