I know it isn't asked but the worst is on the Rio Carbon. The machine makes a humming noise when it has to access the hard drive, but when you're listening to music you don't notice it, and usually it's only for a second. But when you're voice recording, the hard drive is constantly being accessed so the humming continues. So the recording is accompanied by a huge wailing noise that drowns it out. Nice design guys.
Otherwise I love the thing.