User behavior when interacting with a program that responds in 0.1 seconds is drastically different than with a program that responds in 1.9 seconds; see [0] [1] etc. I agree it's not very meaningful to just compute the total number of seconds saved, but on the other hand, the productivity gain could easily be far greater than what that number suggests too.
[0] http://googleresearch.blogspot.com/2009/06/speed-matters.htm... [1] http://www.webperformancematters.com/journal/2007/7/10/accep...
> Put another way: Whether $APP takes 0.1 seconds or 1.9 seconds to do something does not at all change what time I'm leaving at the end of the day.
But it does greatly change how annoyed you leave at the end of day.
Not to mention any noticeable delay in load times will quickly get people to start multitasking, which can easily change a 2s delay into a 2min delay. This can easily ... well it does make a difference.
I noticed this mostly while testing code. After clicking through the interface many times it can easily add up to an hour less actual work getting done that day.
The entire concept of "we saved 10 million hours of productivity by shaving 1.8 seconds off this process" is bunk. You saved 1.8 seconds of productivity n million times, which adds up to not a whole lot of extra productivity.
Put another way: Whether $APP takes 0.1 seconds or 1.9 seconds to do something does not at all change what time I'm leaving at the end of the day.