I haven't had a chance to mess around with it much, but the coz-profiler [1] uses basically the same idea, but the other way around (i.e., slow down everything else to get a "virtual speedup") which helps quantify what the effect of optimizing some code would be.

I learnt about this tool from Emery Berger's talk [2] on this (at strangeloop), which I highly recommend. Lots of really nice insight, even outside of this tool.

[1] https://github.com/plasma-umass/coz [2] https://www.youtube.com/watch?v=r-TLSBdHe1A