I use FireWire a lot. Mostly FireWire 800 when I can. I picked up a bunch of used Lacie external drives cheap last year that have FW 800, 400, USB 2.0 & eSATA so I use them pretty much everywhere possible.
I also have a couple of LaCie burners that have both FW & USB 2.0 and mostly I use the FW port when I can.
I could use a few more FW 800 pci cards. A local shop used to give me a lot of old Macs that people no longer wanted when they upgraded so I've had lots of FW 400 cards and drives for the last 10 years or so. So I've used them over SCSI whenever possible. More convenient.
Computers I have at least 1 of: 128k, 512k, 512ke, Plus, SE, SE/30, Classic, Color Classic, Mac II, IIfx, LC, IIci, Quadras 700, 800, 840AV, 900, PM6100, 6150, 8100, 6500, 7300, 8500, 9150, 9500, 8600, 9600, Beige G3 DT, MT, Server & AIO, B&W G3, Tray loading iMac, Slot loading iMac, eMac, G4 DA, Quicksilver
Mac Portable, Powerbooks: 100,140,145,145B, 160,170,180,190, 520C, 5300,Wallstreet, MacBook Pro
Apple III, Apple II: II, II+, IIe, IIc, IIc+, IIgs