I posted this a while ago but got no responses. A little more searching and fiddling has at least given me a workaround, but I'd now like to know, if this is considered a fault, where to raise the bug report.
Essentially, neither system-config-display nor xrandr will (any more) let me choose a decent refresh rate for my CRT monitor at pretty much any res. (using nvidia drivers). My default is 1600x1200, and this boots into gdm at 85Hz. My login also uses 1600x1200 and uses 85Hx.
However, my wife has sight problems and uses 1280x1024; this comes up (now, was OK in F8) at some really wobbly flickery low refresh rate. *Sometimes* Alt-Ctrl-Plus/Minus will cycle back to 1280x1024 at the decent rate.
I have also found now that 'nv-settings' will show the correct available resolutions.
So the question is: where's the bug? system-config-display *does* have my Iiyama monitor listed, and I can select it (but the xorg.conf it then generates doesn't work for the refresh rates). The xorg.conf I'm using specifies the vert/horiz rates.
But since xrandr also mis-lists the available modes/rates, I suspect xorg more than anything.
The thing I don't know is whether the nvidia drivers can somehow stuff the auto-detection, in which case it's arguably not even xorg's fault.