Hmm... Actually, I looked at the Sil5723 (aka SteelVine) specifications before I went with this board and the product documentation says "Supports ATAPI & asynchronous notification" which I, incorrectly, interpreted as good to go with S-ATA connected ATAPI devices.
(See:
Silicon Image - Product - SiI5723 Storage Processor)
Don't get me wrong, it's a really nice board and works great, but it would have been *really* nice to be able to use the "extra" ports for other things than just RAID. There are some rough edges still to be cleared out from the BIOS but I hope that will be fixed in upcoming releases.