The iomega 320 GB is a very versatile and powerful device with 2 Firewire ports (400 and 800) and a single USB 2 port. It only requires a single cable/interface which provides both power and data bus. It is very quick in all the port configurations and simple to mount and dismount, literally plug and play from the box as of day 1. I use mine to store some 7 GB of data accumulated over 25 year's of work and it is available to me on either Mac (preferable) or PC (haven't tried but see no reason why it would not work) within 30 seconds of plugging in. I use it as an external drive (4th backup copy of my work- not that I'm paranoid) and the data on it is regularly synchronised with my primary drive using SilverKeeper.
And, whilst this last feature is utterly irrelevant, it is so tactile to the touch and so cool to look at and work with that that in itself is reason to own one.
Note: it runs a bit hotter under Snow Leopard (10.6.3) than under Leopard or Tiger.