If you want to win a format war you better fight on all fronts...
That key message looks to have struck home hard with Amazon this year as it has followed up the international Kindle launch and Kindle for iPhone app by bringing Kindle functionality to both PCs and Macs. The PC gets access first (as typically happens with software development) while a Mac version is being "worked on".
As with the Kindle reader and iPhone OS app this means access to over 360,000 Kindle titles will soon come to both these major computing platforms (subject to country-by-country licensing rights) and - perhaps more importantly - will bring cross platform synchronisation. This means users can not only synchronise downloaded content between devices, but also use Whispersync to match up the last page read, bookmarks and even annotations.
Mac requirements have yet to be released, but on the PC side virtually any computer made this decade should work just fine since 128MB RAM, a 500MHz CPU, 800 x 600 screen resolution, Windows XP SP2 or above and 100MB of disk space are all that is required. Furthermore, the application will be completely free on both Windows and Mac allowing aspiring Kindle owners to get started on their eBook collections while they save up their cash/wait for Christmas.
Smart move Amazon. Smart move.