Delkin has released a driver for their CardBus 32 Adapter for CompactFlash that brings compatibility to Mac OS X 10.4.x.
With both a recent-vintage Powerbook 15 inch G4/1.67GHz, and an older Powerbook G4/800MHz (Titanium), a private beta release of the driver has worked like a charm here over the past 10 days or so. We've put it through its paces with a stack of different brands and models of CompactFlash cards and have experienced no card mounting or file transfer problems.
The new driver is only for Mac laptops with OS X 10.4 installed; if your computer is running OS X 10.2.8 through 10.3.9, continue to use v.1.1 of the original Mac driver.
Both Mac driver versions, as well as v1.13.18 for Windows, are free downloads from the Delkin support page.
Update, August 24, 2005: Our email is overflowing this morning with reports that the new Delkin driver enables Lexar's 32-bit CardBus CF-to-PC Card adapter to function in Mac OS X 10.4.x also (the Lexar and Delkin adapters are the same product under the label). Lexar's web site has not yet been updated with an official Lexar version of the driver, however.