When I first worked with the original ASP.NET 2.0 AJAX, some folks told me that it only worked with IE, which was wrong then. I decided to take a look at ASP.NET 4.0 Preview 4 in Chrome and Firefox. I looked at my an example dataview i'm working with in my azure application. Low and behold, it looked the same in IE8, Firefox 3, and Chrome 2 beta. Here's a display of all of them.
Chrome 2 beta:
There may be something that doesn't work right outside of IE, but I haven't seen it so far.