According to the feature matrix, RandR 1.2, NouveauFB, X Render, and Suspend in a KMS environment is now supported across the spectrum of NVIDIA GPUs that are implemented within this driver: the NV04/05, NV10, NV20, NV30, NV40, and NV50 series. X Render was previously supported on earlier NVIDIA GPU generations, but now with the NV50 series the status has changed from being a work-in-progress to being "done". The RandR 1.2, kernel-based mode-setting, NouveauFB, and KMS Suspend features were previously a "W.I.P." across all NVIDIA GPUs, but this too is all now marked off as completed. This is not to say though that the code is all 100% stable and bug-free, but that the feature is now implemented in the Nouveau driver stack.
When it comes to areas of work still left for the Nouveau driver, the Gallium3D driver is still a ways out from being fully implemented, TV-Out is still lacking for NV50 hardware, and there is no power savings support for any NVIDIA graphics card at this time. Other advanced features like any multi-card / Scalable Link Interface support also has yet to be addressed. Hopefully though with the RandR 1.2, X Render, and kernel mode-setting support getting primed, that we will be seeing the Nouveau DRM portion enter the mainline Linux kernel (at least as a staging driver) in the not too distant future. For those wanting to try out the latest Nouveau bits now, much of the latest code has entered Fedora 12.