They are, though they don't feature Dolby Digital Live or DTS Connect.
What this basically means is that the main cool features of the X-Fi, such as the CMSS upmixing, the 24-bit crystaliser etc only work through the analogue output, the digital just outputs as-is.
I don't consider this an issue as it all sounds flippin' excellent over analogue with the CMSS and Crystaliser turned on, but if your anal about digital connection, it may not be for you.