This post goes into a lot of details about their point of view - that the programmer developing software has to run it a lot of times, so if it's inefficient (in terms of CPU cycles) it'll slow them down. I was hoping they'd quantify that, but they don't.

Overall their argument makes sense, but if the slowdown due to "too many CPU cycles" only has a practical effect in taking a few extra milliseconds overall then IMO the programmer isn't slowed down in any practical sense.