I have a 500 G3 B&W with a 29160N scsi card that worked great for a couple of years as long as I was in OS9. Then I moved to OSX.
The Adaptec card simply does not work in the OSX environment.. I downloaded the new drivers from Adaptec (they even have a new beta out since January) but it still, will not allow my second wide scsi drive to be seen. Adaptec did offer support for $69 per issue (a little pricey for an old machine and no guarantee of a solution).
I visited a Mac repair store and they just shook their heads and said the Adaptec cards will not work with any OSX product-period. They did suggest buying a new harddrive because it will be cheaper than another scsi card. So, based on this experience, I never intend to buy another Adaptec product again.