Firewire....i have never used my firewire port on the front of my machine. USB 2.0 is quicker, more universal and backwards compatible, don't bother getting it (FW). It had its opportunity but never really grabbed any market share, much like various other good technologies over the years!
I too have never used my firewire and to be honest all my USB peripherals are USB 1 not USB 2.0 but when and if I replace anything I will definately be looking for USB 2.0. The only person I know who has used his firewire is in to digital movies.