I've gotten about 7 different lists of "Top 10 Reasons Why AJAX is Teh Suck" recently and I have to say that I'm disappointed. They're not quite as well thought out as the "Top 10 Reasons Why Captain Kirk Is Better Than Captain Picard" emails I used to get in 1993. A lot of people are talking about AJAX and, to be honest, a lot of people are doing stupid things with it. It's like when XML (or Firefox, or .NET, or blah blah blah) first made the big-time.
You can complain all you want about not being able to use the Back button on your browser. It doesn't matter. If it's the kind of app that needs a Back button, AJAX is a bad choice of technologies. Just like not every site needs a Flash intro featuring music from "King Missile", not every site needs asynchronous javascript postbacks to an XML web service.
It's a technology that people are still exploring, and we'll find good uses for it ... probably through process of elimination like we always do. I'd be willing to bet that we see 900,000 sites with AJAX once Atlas is released and people are using it. It will be the new BLINK tag.
Random tip of the week: The kimchi stew at Li Hua on Grand Street is the "fullest" kimchi stew I've had, either in New York or in Seoul.