(Since I can't edit this post, I'm replying...)
On my camcorder, I choose the .mp4 files, not the .mts files. I think, without looking at the cam, that they are in a folder on the cam labelled something like DCIM. There is also a PRIVATE fodler. That has the AVCHD files, if I've recorded any. Those can used too if re-wrapped, if I am correct, but I just using the iFrame (mp4) files for now. (Media Converter http://media-converter.sourceforge.net/ is what I use for the AVCHD files. Fast, simple, free.)
We need to have a iMovie HD site somewhere. (The unofficial iMovie FAQ (http://www.danslagle.com/mac/iMovie/) isn't as helpful as I had hoped.