I bought a second hand 505 in the UK. I've never had any problems, and have connected to the sony store for the free downloads. I could read the books already on there (think some of them might still be there ...) and have never had any problems, but to be honest I don't know what the original owner did with it, how much it was used (very little, as far as I could tell, it's still in its warranty period) or whether she ever registered it at all. The books could all have been PD.
I've also never had any problems registering it with ADE, which I use more than the sony software.