Well, I finally ordered the
WD My Book Studio Edition 500 gb external drive.
Looks pretty solid, good reviews, meets my firewire 800 requirements.
I will be partitioning it to use with my windows desktop and my mbp. I think I have the process correctly in mind, if I remember what the helpful Apple genius told me at the store last month.
I'll reformat the entire drive to Windows, then partition what I want to use for my Mac and format that section to Mac OS extended journaled.
I'll backup the Mac probably once a week when I carry it into my office and plug it into the WD. So there's probably not really much to set up in TM.