I have a Sony-600 reader and it definitely works with a Mac. However, the Sony Reader Library software is something that I hate to use to sync my e-books. From the very first day the software was buggy, and for a period of 2 months I was unable to upload any books to my reader.
I recommend downloading
calibre to sync your e-books. The great thing about calibre is that it allows you to convert your ebooks to most major ebook file types. I current convert all my ebooks to epub formats even though calibre does support conversion for the sony native lrf formats.
The one downside of the sony reader is it's reflective screen. If you have direct light on the reader, it is harder to read the screen text. However, I've managed to cope with it, and I really love it now.