I have an external LaCie FW with my Orange Micro card in a beige G3, and I also use it with a B&W G3/Sonnet G4. I am happy with it.
You can't have 2 computers hooked up to it at the same time. At least not yet. I posted the same question a few weeks ago and was told rumor says new FW drivers from Apple may allow this in the future, but not now. With FW being hot swap, it isn't that bad. I can move it to either machine easily.