I don't prefer it, but I've used Final Cut from time to time on my personal laptop, a two-year-old MacBook. It works fine for HD and SD material, as long as there's enough disk bandwidth available. That's certainly going to be your bottleneck if you buy a new MacBook, as there's no option for Firewire or ESATA or anything.
The price difference is significant, obviously, but to me it seems like the MacBook Pro is really the only viable option if you want real-time performance out of a notebook.