First off, I can hardly praise you enough for this tool! Especially being able to try it out with various connections from various locations is fantastic. All in all, it’s very helpful and extremely generous. Thanks, a lot! 
But a few simple user settings would be nice, like turning off parts of the test. Take the image compression test: I fare fairly well with that, I definately don’t need your server(s) to recompress images on every single test I run, so turning that off would make my results page smaller while being a small relief on your servers… win/win, right? Same goes for the GZIP test.
Obviously all should be enabled by default, but 90% of the time I’m mostly interested in the waterfall 
So IMHO it would be fantastic if that wasn’t just configurable, but if those preferences could also be saved in cookies (something like “save as defaults”).