The solution works great with cassini but as soon as I make it run into IIS (7.5 on Windows 7 / 64), it stops working. All js & css file are never downloaded and the script fails. I looked into the MiniProfilerHanler, the GetHttpHandler method is called for each required js & css but the ProcessRequest method never runs.
The same behavior is observed using the sample.mvc project that goes along with the mini profiler sources.
I went to Program/Feature control pannel and clicked add remove windows feature. There I saw that under IIS, ASP.Net was not selected (all my sites worked like a charm) and checked it.. and Voila ! Don't ask ;-)