To expand on BlackVoid's answer--
If you do buy a SD card for your 505, Windows will see it as an additional drive--essentially using the 505 as a card reader. You can transfer files to and from the card when you have your 505 plugged in directly through Windows Explorer. You can also use the Sony Reader software to transfer files to the card. This will alleviate the first loading/font size changing times BlackVoid is referring to.
dordale