Rob, your render time is because of the format you are ripping it to, it requires a complete re-encode of video frame to render. What did you rip to? iMovie can definitely handle this… if you tried it in Final Cut Pro, you must have tried it on your Powerbook?
By the way, when you output from FCP what format you choose to output to could GREATLY affect your render time. There are faster encoders if you are just trying to get a good enough watch quality.