I've just got a JVC DV4202. It only takes a few seconds to scan the disc, and I've got a full 4.5 Gb on this disc.
It's kinda ignores any folder heirarchy you put on there, by which I mean that you can't choose to explore a top level foler (ie Artist) and then pick a lower level folder (Album). It just assigns each folder an number and you go direct to the folder number.
Now that I know, I'm gonna put another disc together with the folders numbered to start with. That'll make it a damn sight easier to navigate.