For NV40, it should generally work, with rare exceptions, NVAA/NVAC should be in good shape too. Kepler is largely turned on because it does work fine for a bunch of boards, but there's another bunch for which it won't. But seemed like the nice thing to do was to let users try and see which bucket they're in.
For all of these, it's still manual switching through /sys/class/drm/card0/device/pstate -- no automatic switching yet. (That'll happen after switching between levels works reliably.)