The PQP profiler from Particletree is a very handy thing to have in your development toolbox. However, it doesn’t deal with the ever-increasing amount of work done via Ajax requests. Or, at least, it didn’t.
The Prototype library has great Ajax support. Two features in particular allowed me to implement this new functionality extremely quickly: it adds a header that identifies requests as being of type XMLHttpRequest (as does jQuery) and has a global responders object (which jQuery lacks) that means any Ajax request created can automatically have the required callbacks registered. In short, you won’t need to change your code – as long as you’re using Prototype as well that is, although I’m sure one of you clever jQuery types can knock something up fairly quickly!