I have also enjoyed the Scout service from Saucelabs. It is a fully in-browser experience. They do all the VM work and stream you the screen. Full Disclosure:

I have also enjoyed the Scout service from Saucelabs. It is a fully in-browser experience. They do all the VM work and stream you the screen. Full Disclosure: I am friends with one of the founders and was in a promotional video for saucelabs.