Interactive websites using AJAX

I've heard a lot of buzz about this new way of using JavaScript and XML to produce some really powerful web pages with AJAX (Asynchronous JavaScript and XML). Before I continue, you can see AJAX in action at Google Maps (beta), Microsoft Start (preview), Google Personalized Homepage and Gmail if you haven't heard about it yet. These interactive sites are very easy to use and appear to response much faster than traditional sites since the entire page is not reloaded after each item is clicked. However, AJAX has some problems that might really annoy users. The problems listed below are very similar to problems found in websites using Flash...

1. It doesn't have an alternative view if your browser doesn't support JavaScript, similar to running a browser without the Flash plugin.
2. The back and refresh buttons don't work (by default) in your browser
3. It doesn't change the URL in the address bar. This prevents bookmarking a page. Google has addressed this issue by providing a Link to this page feature on Google Maps that redirects the browser to a URL that can be bookmarked.

By the way, I've still got a bunch of invites if anyone wants to try Gmail, the best free webmail IMO.