Luckily Mike brought his Raspberry Pi3 computer and with my pico projector, he was able to show how responsive the RPi was, running Ubuntu Mate (not very responsive) and then the Kodi distro ( quite responsive). :-)
I was inspired to test my Pi3 at home after our meeting, connected to a 1080p monitor. My version of Ubuntu Mate (16.04) is truly awful; I wouldn't call it usable at all. Kodi (also an old version) is more responsive, but when I tried to play a video residing on my usb stick, the playback was jerky.
I thought about this some more, and I'm now asking myself whether booting from the usb stick does make it faster, since the port it is connected to is only usb 2. It might have been a few years ago when SD cards were very slow, but now you can get them with read speeds above 100 mb/sec; about 4 times what you can get out of anything attached to a usb 2 port. The second consideration is the age of my distros, as newer versions are supposed to be more optimized for the Rpi. The third is whether Ubuntu Mate is as good as Raspbian on a Pi. Since Raspian is what is being pushed by the foundation that makes the Pi's, I think it will run better. The fourth is whether my booting system, berryboot, is any better than noobs. (Berryboot is good for setting up with multiple distros on the same volume.)
At any rate, our PLUG MUG has motivated me to dust off my Rpi, try a few things and report back. Incidentally, I read a review of the Rpi 4 in Linux Pro. It gives it very high marks, but notes that there are a few things in the hardware that don't work as well as they should, that they expect to fix in an updated version. I'm glad I read that because I'm would like to buy a Pi 4, but now I think I'll hold back a few months. The biggest advantage to the new model, as far as I'm concerned, is that it has two usb 3 ports and is now set to boot from usb (without having to init from an SD card, which is how I get my Pi to boot from usb). Those changes will make a Pi into usable desktop computer.