We haven't been able to test the S3 Graphics Linux drivers due to troubles actually finding S3 Chrome 400 / 500 hardware, but we have been talking about their "magical driver" for two years since they mentioned OpenGL 3 support and even Blu-ray and Microsoft DirectX 10.1 support for Linux. It turns out that S3 was indeed working on a new Linux driver, but it was missing in action even when the Chrome 540 GTX launched, but it ended up coming months later than expected.
There was no Blu-ray / DirectX support (likely this was mentioned due to uninformed S3 PR folks), but it was eventually released with support for OpenGL 3.1, VDPAU H.264/VC-1/MPEG-2 video acceleration, RandR, and even kernel mode-setting. This came by October of 2009 when S3 Graphics also brought x86_64 Linux support as up to that point their binary blob only supported the 32-bit kernel.
While this gave us some hope for seeing better S3 Graphics support on Linux, since that last 2009 driver release there has only been one driver update from them in 2010. This most recent driver update brought support for Fedora 12 and bug-fixes, but no major feature advancements. At that time, Fedora 12 was already succeeded by Fedora 13, but S3 ended up just hitting F12 support at that time. The bug-fixes in this release included Xinerama failing under certain conditions, system hangs, video playback problems, and other issues.
Unfortunately with the lack of recent driver updates, there is no S3 Graphics Linux driver support yet for Ubuntu 10.10, Fedora 13/14, Debian 6.0, or any other recent Linux distributions. This driver is designed to support the S3 Chrome 530 ULP, Chrome 540 ULP, and Chrome 540 GTX. There's also embedded S3 ASICs including the Chrome 5300E and Chrome 5400E.
It's too bad that S3 Graphics doesn't put forth more effort in their binary Linux driver or provide any open-source support (or be friendly to the open driver community like with the S3TC patent situation), but at least they are doing something. If there is actually anyone with S3 Graphics hardware on Linux, let us know in the forums how the driver and its advertised features are actually working.