Well let me dig up my test results spreadsheet from when I first got my 2500K CPU, times are in seconds to complete my task in Visual Studio 2010, first set of numbers is the system at stock clock, second set is overclocked at 5GHz, during my game development most of my day consists of building the game, loading the game and testing out changes or additions, therefore the reduction from doing that in 32s vs 21s is absolutely huge, even doing code changes that don't require a total rebuild I am waiting 3s less. It may not sound like a lot but when you are focused any time saved is very important, you can only be focused for so long.
build debug from clean 12.9 6.9
built already, go and load all effects and units 8.2 5.6
at title screen all loaded, start medium map 19.6 14.3
modify main.h build load to splash scrn 3.4 2.1
modify main.h load into medium map 31.9 20.9
modify main.h optimal load no sound, small map 16.9 10.3
running in game, modify main.h apply changes 10 6.7
average 14.7 9.5
system is 2500K, C300 SSD, 16GB memory