It was 2 years back where my first AJAX framework had been deployed at my previous company. The framework had a big vision and had achieve a pretty magical result after deployed (and it is still running today, although phasing out probably in another 1 year time).
The unique feature of the framework is that it supports template for multiple items listing. Which you can add/edit/remove a row, entirely on the client side, without having to postback to the server at all. The framework do comes with some drawbacks, it is pretty slow when the page is big and there is some memory leaks which will crash the IE after some many AJAX calls.
With that in mind, I'm now back to my vision to re-create the framework from scratch now, again. This time however, I'll be writing everything from scratch including my AJAX processor page, which previously I've used AJAX Pro. More details will be posted and let's see how it goes.
Another issue is browser compatibility. I wish I can ignore it, but I can't now simply because my users now will be the general internet public. Well, I don't have many PC to test out, but at least I have Firefox and IE7 and I got to ensure it works on both of this.