Unfortunately, Apple seems to be marginalizing widgets. Submissions to the Dashboard area are failing (no updates since 2010-12-03) and the Apple web page doesn’t provide convient navigation. They are focusing on the Mac App Store, which doesn’t appear to allow Dashboard Widgets, just full fledged applications. I’m not so sure a full application is good way to get a clock.
Meanwhile, integration as a Chrome App is going well. Of course it suffers from similar issues – choices are a full tab, or a floating panel in it’s own window. Which would you prefer?