Ubuntu is including the DRM code that, if mature enough, will be able to run compiz. If Ubuntu is shipping it in 10.04, I'm sure that we'll see nouveau DRM in Fedora 13 too. I'm just a little surprised that Ubuntu is taking the initiative. Very happy, too, because they have a huge installed base.
F12 already has the latest upstream nouveau code, there's nothing further for Ubuntu to ship than what currently exists in Fedora. What's missing is the nouveau 3D drivers, which are missing for a good reason, none of them are ready yet.
That said, if you're on NV40 (GeForce 6/7) or NV50 (GeForce 8 and up) and feel brave you can install the 3D drivers yourself. They work somewhat, enough for compiz at any rate.
It'd be great if this worked as I'd like to try an X session over a multi gfx card Wayland session in order to try and get a composited desktop with two gfx cards instead of having to resort to xserver-xgl over xorg to achieve the same thing.
xgl isn't maintained anymore and so running current Gnome or KDE on it presents some difficulties.