Excerpt: I got a new iMac with Thunderbolt ports and I still need to use my external FireWire drives. This adapter does just what it's supposed to do. Just plug it in and everything works. No configuration needed.
Excerpt: I bought this product for use with an Apple iMac. I have several external Firewire devices (both firewire 400 and 800) and needed to be able to connect them to the computer via the thunderbolt port. I tried the adapter with an external hard drive, scanner, and DVD burner and all worked perfectly. Be aware that using this adapter with a firewire device knocks the speed down to the speed of that firewire device; you won't get the top thunderbolt speed.
Summary: When Apple decided to eliminate the mini-DVI, Ethernet and Firewire ports on their new MacBook Pro laptops (three ports in total) and replace them with just two Thunderbolt ports, they created a dilemma for many MacBook Pro owners - myself in particular - trying to upgrade their systems. My MacBook Pro is the hub of a desktop system that includes Firewire drives, Ethernet connectivity and an Apple LED Cinema display.
Summary: Bus power is too low. I'm a photographer and need to daisy chain 2 drives on set, without AC power like I did when running firewire in the past. Very poor design that doesn't consider professionals.