i have never used a portege, but one of my best friends has a toshiba laptop. he likes it, but its monstrous compared to my ibook (900mhz G3).
The thing is, you aren't being very clear about your needs....do you need windows? do you need the G4 for photoshop, etc?
You said you needed firewire, and since its not terribly likely (although not impossible) that someone on these boards coudl tell you when/if the r100 is getting firewire, i would say go with what you need now. If you need a computer wiht firewire, are comfortable with Mac OS X, and can move away from windows, go for it. If you can't leave windows (software reasons, etc) and virtual pc doesnt work for you, then keep looking i guess...i know fujitsu makes some smallish computers with firewire.
--carly
ps the ibook is also almost a 1,000 cheaper than the r100....if you are looking to spend more, and gain portability, have you thought about the 12in powerbook?