I have read that when using an external device - USB stick or Ipod etc it can take a little time to read all the info - however next time you connect the same device if nothing has been changed it will read the info a lot quicker. wife has copied across music from Itunes onto memory stick and has not reported any problems using it. Also with the quick play I have had with the system I really like the controls built into the steering wheel - a lot easier to use then on a stalk like they were in 207. Changing radio station is really easy with the list and scroll wheel option.
Depends on how you store the music I guess - we use Itunes which creates an Itunes folder on your computer. Each album is then downloaded into it's own folder within that with each track within the album folder. When you have your library listed in Itunes you can also get Itunes to downlaod the Album artwork - even if it is music you have imported on to your computer from CD and not actually purchased from Itunes. This then tags the artwork to the Album. To copy the music on to USB stick you can just copy the folders for each album you want included. Then when you plug your memory stick into USB port on car it reads the info and displays the Albums - think it shows six on screen at once and you just scroll through to which you want.