We have had a number of customers ask us if the Delock 91694 FireWire 800 CompactFlash Reader works under Mac OS X Yosemite (10.10+). Since we are still running 10.9.5 on our machines, we obtained an extra hard disk, attached it using a Delock Thunderbolt Dock, cloned our system, and then upgraded the clone to Mac OS X Yosemite. Delock's 91694 FireWire 800 Reader worked just fine, mounting two different SanDisk Extreme® CompactFlash 60MB/s UDMA 16GB cards.
Under 10.4 through 10.9 iPhoto would open automatically when the reader was connected or when a new CompactFlash card was inserted. Mac OS X 10.10 Yosemite features a new app called Photos, and its behavior is somewhat different in that it did not automatically launch. However, when we opened Photos and navigated to the import function, the CompactFlash card present in the reader was there and ready for importing.
By and large, we can say that we had no problems with the Delock 91694 FireWire 800 CompactFlash Reader under Mac OS X Yosemite (10.10+). Obviously your mileage may vary. We will test the under Mac OS X El Capitan sometime shortly after it is released. Here is a screen shot of the reader working under Mac OS X Yosemite (10.10+). Our MacBook Pro has a FireWire 800 port and a Thunderbolt port.