I just received an e-mail from Dan, Initio's support guru, letting me know that indeed Initio has released beta OS X drivers for their Miles UltraWide SCSI board (PCI). I have been awaiting these since before the public beta and must say, they seem to work like a charm! It's quite nice having access to my 10,000 RPM UW drive again!
I'll reiterate that they are beta drivers, and as such have some stated limitations: they only support hard disks at this time (no other SCSI devices), you cannot boot from a connected drive, and "deep sleep" mode is not supported. However, Dan tells me that he has had a user report indicating that there was a lucky user who successfully installed OS X on his SCSI drive and did see that drive boot the system. I will give this a shot soon, but ant any rate, expanded functionality will no doubt arrive in driver updates.
The firmware update for the Miles board can be found in the Drivers section of Initio's Site. Drivers for Initio's Bluenote and MilesU2W boards will soon be released, as well.