I can't answer all of these, but I'll do my best to answer some for you, until someone else drops by.
1. I don't think so I'm afraid. I think it will only play within the folder you are in via browse mode.
2. The UI is pretty nippy. Not as fast as the latest mobile phones, but fast non the less.
3. You can favourite tracks. They get saved into a special favourites playlist.
4. I would recommend getting one of the Questyle cases to protect the unit. I have also purchased some wipe on liquid display protector to prevent the gorilla glass getting covered in little scratches. Not everyone bothers, but if you're going to have it in your pocket all day, I reckon it's worth paying a little extra to keep it looking tip top
Hope that helps.
Thanks, that answers most of my questions.
Can anyone confirm if there is functionality to auto-advance to the parent, or sub folder after playing all songs in the folder it's playing from?
Also can somebody confirm if there is a way to actually add stars or meta-notes to files, rather than a favorites playlist?