At work I have a dual 2 GHz G5, but at home I have a Mac Mini with a single 1.25 GHz G4. FCP 4.5 on both machines, and I edit DV resolution. It’s not about to set any land speed records–I can definitely tell it’s slower if I’m paying attention to it. But if I’m just editing, I don’t notice.
What I do miss is a lot of things being realtime on the G5 that aren’t on the G4. No problem, really. I’m always editing from external drives and I walk them back and forth between office and home on occasion. If I edit something on the G4 that needs a lot of realtime effects, I just don’t render them. When I have the drives at work to lay off to tape, the beefier processor means no render’s necessary.
Maybe a similar semi “offline/online” edit situation would work for you?
I also use After Effects on the Mini. Renders aren’t great, but it’s fine to use. (Renders give me an excuse to take a lunch break, too.)