So Google announced this yesterday, but pushed implementation to today (11/29/07). I installed it as soon as it was allowed.
This is not quite what I expected....
Although useful, the gadgets available for OS X implementation are not as available as they are for iGoogle, which I use frequently to monitor different data sets and to do lists.
However, even given this, it will make development a since for people wanting to hit both the OS X dashboard and the Google desktop markets.
The installer is only available through the "Google Updater.app", which comes with the 1.4.0.838 build of the Google Desktop for Mac OS X.