Microsoft finally has officially unveiled the office web applications.
Micrsoft has guaranteed that it will work with Mac and Windows along with firefox users.
Microsoft will also be providing the mobile version, but it is meant only to support viewing access.
You can find the more info at microsoft website. Microsoft has removed the link but can be found using google cache at http://126.96.36.199/search?hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&hs=j2Z&q=cache%3Ahttp%3A%2F%2Fwww.microsoft.com%2Foffice%2F2010%2F&btnG=Search