Seems like performance and tweaking HTML is on Microsoft’s mind at the moment. They just released a new AJAX performance tool, really a AJAX re-writer that requires IIS7.
http://blogs.msdn.com/somasegar/archive/2009/04/29/vs2008-ajax-profiling-extensions.aspx
Not tried it my self yet as it requires IIS7 (and I dont have any dev VM’s handy at the moment), but certainly looks interesting. This in conjunction with the pretty cool standard feature of IE8 Profiling (IE8 profiler. I have to say this unsung feature definitely rocks as part of the standard tools (yes I am very aware of FireBug 
), but as awesome as it is – it is a add-on. This is owned and controlled by the MS browser team, and shows that they are starting to act on what people have been telling them for years.
Definitely seems performance monitoring is a keen focus at the moment.
Gareth