I have the 30GB model, which was the top-of-the line at the time I bought it. Since I got it, I've used it for a solid 8 hours a day for 6 months.
I love it! I'd marry it if that were legal.
To hell with the law. My iPod is now Mrs. Cocoamix, and we shall have smaller flash-based MP3 players as children.
Firewire is a connection type that has speeds of 400mbps, or approx 50 Megs/sec. In the PC industry, it's also called IEE1394, and Sony calls it iLink. It's used in Digital Cameras, Hard Drives, Audio/video devices galore, and even scanners.
The advantages besides the high bandwidth (it is 80mbs slower than USB2, however) is that it is a fully powered Bus, meaning that it supplies power enough for a hard drive (USB2 usually requires an external adapter to provide the power needed by many devices).
What this means is that theiPod charges whenever you connect it to your computer. The entire library of 30 gigs can be downloaded to the iPod in about 15 minutes.
Most modern computers have Firewire ports. If not, PCI Firewire cards can be had for as cheap as $10.
You can find more info here:
http://www.ipodlounge.com/
and you can find goodies here:
http://www.everythingipod.com/
You can use the iPod as a portable hard drive. You can buy modules for voice recording, flash-card readers, FM trandmitters, and other stuff. It holds your contacts, notes, and has some extremely boring games as well.
They make tons of cases for them, but I keep mine clean by licking it.
Give in to your lust.
You can always go the ebay route, but bargain hunting for them is similar to bargain hunting for any electronic goodies. Just keep your eyes peeled.
Still, not much fun to have to shell out 50 quid after a year and a half. 
