I never use the Sync feature. It would be nice if it did work as I have two Sony Readers, but I'm not adventurous or patient enough to try it. ;-)

Mostly I use it to download purchased books. I normally just copy the book to an SD card rather than use the reader software to transfer them to the 900, but I have to use the Reader Software with my 300. I thought about selling the 300 since I rarely use it since I got the 900, but the 300 will make a good travel companion due to its small size.