Just took the sparkling new browser from Google - Chrome - for a spin in the umbraco UI and it works as expected - perfectly. I was able to browse the tree, use the right click menu and edit using the tabs and all the existing controls including WYSIWYG without problems. This once again proves that even though umbraco has one of the most advanced UIs in the world of Web CMS, we're also one of the most cross-platform/browser compatible Web CMS's.
Google Chrome is an insanely *fast* browser. Umbraco really excells and load times and rendering of different views is really, really fast. I'm very excited to finally see a browser that hits the market made by people who actually develops apps and sites for browsers. This browser is much more "invisible" than any other browser, leaving space and screen estate to what matters, the apps and sites you're using.
This blog post is written in umbraco 3.0.3 using Google Chrome, so that's a living proof that it works. Umbraco 4 looks and performs even more stunning with Chrome.
UPDATE: There's tree quirks in Chrome (and Safari) as reported in the comments. It'll be fixed for Umbraco 4. Thanks for the feedback!