I just bought the same camera and there are various options you can pursue:
1. you can copy the video directly from the camcorder drive (warning: the manual strongly urges you not do this as it may “damage the camera/video”) but I do it anyway.
2. if you are using iMovie, you need to understand that iMovie 7 doesn’t natively support .mts files (Canon format) so it actually “plays” the video and converts it to .mov format during the import process.
So you’re dilemma will be: import the video very quickly by copying the files over from drive to drive but you’ll be left with unreadable .mts files or you can import it via USB via iMovie but it will take longer.
The compromise I came up with was to copy the video from drive to drive and use Sony Vegas to edit the video as it natively supports .mts file formats. I run Vegas in a windows Xp virtual machine and it is a bit slow even with 4 gb ram on my Mac.