Bought an A500. Now What?

[_stet_]

A free alternative to the AF/AmigaExplorer route is transwarp. I use it all the time to transfer ADFs using a null modem cable & cheap USB-serial adapter.

Here's the homepage for transwarp & ADF Sender Terminal:
http://adfsender.stoeggl.com/
Here's info on how to get transwarp over to your Amiga:
http://adfsender.stoeggl.com/adfsenderterminal/methods.html

Transwarp is also part of the free "Hombre" package (which includes several other utilities related to ADF transfer with an A500). You can read about it here:
http://wiki.abime.net/transfer:hombre

Re your question about HD disks, my understanding is that it's just a reliability issue. Data may not survive as long on an HD disk formatted as DD as it would on a true DD disk.

Hope that helps.