I only got the wifi model, not the 3G/Whispernet model.
I figured you can fit 3500 books on the thing, I can download them at home, load them up and its good for a while.
Got mine direct from Amazon as well.
Also Pete, the new generation has a pdf viewer built in as well, and there is a program called Calibre that will convert any text you want into e-book format that you can read on the Kindle. So yes, you can buy the books on Amazon (which are about $10 compard to say $25 at Borders) or umm *cough* T*rr*nt *cough* and use calibre to convert.