Just fell in for the new Sony NW-HD5, even better than the HD3, battery life is now up to 40 hrs and the battery can be removed by the owner.
The only issue I saw for the time being is that you have to use the proprietary software to convert and transfer musical files (works only on Window PCs), even for existing MP3s (I don't mind as I'm actually ripping my CD collection) I did have some trouble on XP, but it works fine on an older Windows ME machine.
Prices on the older NW-HD3 are going down these days.