Hello,
this is just a field report. I tried an install on an ASrock 4CoreN73PV-HD720p motherboard, which sports onboard a GeForce 6250 with shared memory. This installation is meant to work on a sony trinitron professional CRT screen commercially rebranded as IBM P275 with 1600x1200@85Hz.
Livecd: strange triangles and shapes drawn on plasma desktop, sometimes desktop hangs, resolution ok.
Installed: at the end of boot, after splash screen finishes, plasma desktop does not show panel and then also background disappears, leaving a useless mouse pointer around, which does no action, resolution ok.
I therefore installed a GeForce 7300GT on pcie16 bus, resulting with exact same problems.
Putting in place of the 7300GT a Quadro 2000 card solved all problems.
Clearly, although at
https://nouveau.freedesktop.org/wiki/FeatureMatrix/ it looks like that Curie family (NV40) should be ready for production, only Fermi family (NVC0) filled up the bill.
This happened only when combining noveau with plasma on siduction, as other distros I tested, like partedmagic, correctly visualized desktops at 1600x1200@85Hz with noveau BUT without plasma on the Curie cards.
This leads me to think that, more than a bug within noveau, it's something that has to do in the way plasma interacts with noveau on certain hardware.
Hope this helps some progress.
THX