The 405 takes less time to charge than the 605, but it is still a few hours. Mine has charged, in the DVR station, in 3-4 hours; add an hour or so if you are charging via USB.
Music sounds pretty good and having the ability to swap out SDHC cards with various media is pretty nice. I would suggest looking for a 404 though as having a full 30gb at hand rather than various capacity SDHC is nice unless you really like swapping cards.
The Battery Dock is nice too as it really expands the play time if you watch a lot of video, if music is your thing then don't worry about anything other than a good case. The 405 is really light too.