When is it appropriate to use AJAX?
what are the pros and cons of using AJAX?
In response to my last question: some people seemed very adamant that I should only use AJAX if the situation was appropriate: Should I add AJAX logic to my PHP classes/scripts?
In response to Chad Birch's answer: Yes, I'm referring to when developing a "standard" site that would employ AJAX for its benefits, and wouldn't be crippled by its application. Using AJAX in a way that would kill search rankings would not be acceptable. So if "keeping the site intact" requires more work, than that would be a "con".