Before all Creative X-Fi sound card owners go and download this driver, it was written by Takashi very quickly and is based solely on the Open Sound System's code. Furthermore, Takashi doesn't have an X-Fi sound card so he doesn't even know if the driver will do anything at this time. This new Creative X-Fi driver for ALSA should be considered highly experimental. This driver can be obtained through git and the details are described on the ALSA development mailing list.
Takashi had only begun porting the X-Fi driver to ALSA that morning. On the ALSA mailing list he describes the sbxfi driver in OSS as being "half-baked" with a number of limitations, but as the code is short, it's easy to port even without Creative's APU documentation.