drdimento,
Just FYI, the G5 went away long ago. Its successor is the
Mac Pro (your purchased a
Macbook Pro). The current Mac Pro offering, the "base" model, is an 8-core 2.8 GHz Xeon machine. There are four hot-swappable drive bays which would have you "sittin' pretty" as far as additional storage goes, as well as booting into Windows (you could have a dedicated drive for that). But nahhhh, it probably wouldn't make your work any faster, would it? 😉
I'll tell you, I really like the WD Mybook Studios. They have a triple interface, FW 400/800, USB, and eSATA, and come in 500 GB and 1 TB capacities. You can get a whole lot of bang for the buck, without going further than Best Buy. If you pay attention, you can generally pick one up while it is on sale. I'm not going to nay-say the drive you have linked, but I would rather spend that $$ on something that would give me more. Now, the Mybook is certainly not portable, or not as much as the one you linked. If you are dead set on truly portable external drives (and I consider this incompatible with serious video production), you'll end up spending more for less. Don't get me wrong, I have at least one small portable (bus powered) drive myself, but I couldn't see myself using it for serious media storage and manipulation.
Scott