Thanks all for your replies
I bit the bullet and ordered a Sony PRS600 from the US. It arrived an hour ago (just over 72 hours after ordering, how quick is that?) so I haven't used it yet - it's charging at the moment. I have downloaded calibre and am hoping to have a play with it tonight.
I hadn't fully realised how much cheaper it would be to purchase overseas, it was only AUD260 incl. shipping
I am very excited to make my first steps into the hopefully wonderful world of e-reading!
thanks again for your help