I've just watched the video introducing Firefox's TabCandy:
Much of what is presented is not novel - but novelty is not the heart of innovation. Execution is, and TabCandy looks like it has a great chance of taking off - the Firefox userbase and the simplicity of the user experience.
Bing's whole approach to differentiation has been to focus on tasks, and a big part of TabCandy is to help the user scale over tasks, especially those with a long term nature. Should the browser embrace the information sources, or should the search engine embrace browser like state?