I may be the last person to notice this for all I know, but I just plugged my FireWire-based Focusrite Saffire into a MacBook Pro 17″ and was treated to a blinking light show. The solution? Don’t use bus power; plug in the Saffire’s power supply to an outlet to power it directly. The solution is detailed in Focusrite’s support document, and I expect applies to some if not all other FireWire bus-powered devices, as well:
The LEDs on my Saffire flash when the unit is connected to my MacBook Pro. Why?
So, I wonder why Apple chose a lower power spec for FireWire — or, if indeed they chose it all, given that the Intel Macs have specs very much inherited from the PC world. (For the record, though, my MacBook is fine.) The MacBook Pro is a fantastic machine, but at least now you’ve got this heads-up.