I have a Sun W2100z running Solaris. It's a fantastic machine, but the graphics has never been too hot. It's got the entry level graphics card - an NVS 280 if I remember correctly - and I've been using the bundled nv driver as I wasn't aware that the accelerated driver could do much better.
I was trying to get DVD playback to work, and gxine seems to work (after I had built and installed libdvdcss), but was rather slow and I noticed that Xorg seemed to be pegging a whole cpu. In addition, it might be neat to get Looking Glass to work.
So I ambled over to NVIDIA and their Solaris Driver downloads, and noticed that my graphics card was listed as one of those supported. I downloaded and installed the latest version (9764), and that didn't work. I get an error message as it boots that seems to be from the nvidia driver, but then the system immediately reboots. Not good. (I went into failsafe from the grub menu and used pkgrm to delete the two packages to recover.)
Then I had a look in the forums and noticed a message about a legacy release (9631). Now, it doesn't really explain what the legacy release is in this case (the information on the download page about legacy releases applies to Linux), and there isn't a link to the legacy release on the download page itself, but to cut a long story short - the 9631 legacy release works fine on my entry level box. DVD playback is a bit smoother, although still not brilliant, but the cpu load is pretty negligible compared to before.
If you, like me, have an entry-level W2100z with an NVS280 graphics card, then you may be advised to use the NVIDIA legacy driver rather than the latest and greatest.