Hi Jah,
Yeah the wind up function isn't really feasible if you only want to listen to DAB. It has an internal battery that when fully charged will give you about 6 hours of mains free listening. That should be more than enough for most situations.
It also has a completely separate FM tuner which is where the wind up bit comes in useful. A few minutes winding will give you an hour or so playback, so it's really good if you suddenly find yourself without power.
I have one, and think that at £40 it's a bargain. Cost more than twice that when I got mine. You can pick them up at any Currys or CurrysDigital store or online here
http://www.currys.co.uk/martprd/sto...null&sm=null&tm=null&sku=868381&category_oid=
Hope that helps!