Dear Cooters, especially those with Nvida cards.
After talking about antialiasing with Stuart McNicholas, I discovered a
program called nvidia-settings.
I found that if I do:
Antialiasing Settings -> Override Application Setting, and set the
slider to 16x
then I start Coot, I see that it starts up in nice antialiasing mode
(which is a lot better that the poor mode that Coot has built-in).
I don't know if this works on other/newer systems, but it works for me
on my oldish GeForce 6600.
(Of course the FPS takes a hit.)
YMMV.
Paul.