I have just posted a small command line tool on the Esri resources website. It’s similar to MXD Perf Stat but hits cached/tiled map services. It can also be used to simulate load by spawning multiple instances to hit the server at the same time.
I’ve been looking for something like this ever since we had “performance” issues at a client site (even with cached map services). I never found one so decided to write my own.
Anyway, it may be of use to someone in the future.
Geodatabase Geek 
I like this tool and have recommended it to people in the past.
Any chance you are going to put together a video or some screenshots to showcase how to use it, and to really show the benefit of it?
Hi Simon, glad you like the tool – I hadnt considered a video, I spent a fair bit of time creating the document that is included in the download now. Have you seen this document? It has plenty of screenshots and even a real world use case from a recent project.
My mistake – yes I do remember that document. If you have time, maybe squeeze some of those screenshots into this blog post? I teach Server Admin, and hope you dont mind, but recommend this tool.