I just noticed that Adaptec has released revised (beta) drivers for the 2906, 2930, 29160, and 39160 SCSI cards. If you've got one of these, head on over to Adaptec's OS X beta page to download the driver. They've also provided an email address for beta feedback: OSXSCSIfeedback@trillium.adaptec.com.
I'll be testing the 2930 driver tonight!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010423181327597