Glad you got something to work. I think I had a brain fart this AM but I'm much better now
I had a "slow" system with the 2.4.20 series when I had ACPI on. When I turned it off, things got much better. Don't know if you put ACPI in the rc2 but if you did, you might do the acpi=off and see if it runs better.
You're right that the 1.x and 2.0 NF7 series used different chips. It took a long time to get the 1.x series BIOS sorted out, maybe it is taking some time for them to sort out the 2.0 version.
Sorry your X isn't up to snuff. I presume you reloaded the new Nvidia driver. If it was having problems with GLX, you might look to see that the following links got done in the install as they are the glx libs used with the driver:
/usr/X11R6/lib/modules/extensions/libglx.so -> libglx.so.1.0.4496
Glad you're up and (semi-)stable. It can be frustrating getting there but when the box runs for months without a hickup, it's good!