Let me stress this first: I’m very interested in Ajax, and I definitely like the final result and the impressive UI improvements it brings. However, I can definitely smell a lot of hype around it: two different (instant?) books, (pseudo) libraries showing up, countless blog posts, coffee machine discussions, third place in a google search for the term “ajax”, all that is somewhat worrysome.
Combine this with a not-so-strong foundation (does really XMLHTTP, an emulated ActiveX hack, qualify as a foundation?), limited cross-browser compatibiliy, and a real danger of spaghetti code and tangled webs of unmaintainable stuff: the final outcome I can expect is either a large success in the low-end market or a huge hype going to fade pretty soon. I definitely plan to keep an eye on it, and even use it (actually we already did) in very specific scenarios, yet I’m afraid Ajax is going to grow as a set of hacks rather than as a sustainable and long-lasting technology. But time will tell.