It really is a shame that FireWire didn't work out. Aside from the far better transfer speeds, when used for external storage FireWire has always been more solid. USB storage has a nasty habit of periodically flickering out for a split second and has generally been more flaky, something that's actually gotten worse with USB 3 — if you haven't run into this set of issues yourself, do a quick Google and you'll find mountains of posts from people having major issues with USB 3 where 2 works great.
Naturally this extra speed and solidness made for a better experience when booting from external media. One my favorite features of my 4th gen 20GB iPod was the ability to keep an OS X partition on it that I could boot from via FireWire. It worked great — well enough to get work done with, even on low power machines like 400Mhz G3 iMacs — and it saved me several times.
Also, I always loved that little click when plugging in FW400 connectors (can't remember if 800 had this feature). That little bit of tactile confirmation that you've plugged your device in properly is something I wish USB had.
Naturally this extra speed and solidness made for a better experience when booting from external media. One my favorite features of my 4th gen 20GB iPod was the ability to keep an OS X partition on it that I could boot from via FireWire. It worked great — well enough to get work done with, even on low power machines like 400Mhz G3 iMacs — and it saved me several times.
Also, I always loved that little click when plugging in FW400 connectors (can't remember if 800 had this feature). That little bit of tactile confirmation that you've plugged your device in properly is something I wish USB had.