Your iBook certainly meets the minimum requirements. I've edited video on 300 MHz G3, and also on an 800 MHz G4 and you should be fine for most things. No doubt you will be somewhat limited in the number of real-time effects you can do, but that shouldn't matter.
The one area where you might want to seek more horsepower is in compressing your movie, say for distribution on the web. Even a 5 minute video may take half and hour or more to compress down from DV (depending on the settings and codec).