I've probably done at least 500 re-installs of Windows during my time.
I did start at an early age, but none the less a lot of hours has been spent just setting up a machine. I've learned a lot, of course. Not by re-installing - but the reason for re-installing was often because my curiosity took me places where I ended up crashing the system.
But Windows is slowly becoming me secondary OS, and I got a new Mac today to replace my MacBook Air and needed to prepare it for web and iOS developement.
I'm probably not done yet, but I started with a small check list for setting up a Mac for web development and forked the repo to my own account, and added a step to configure a Mac for iOS developement.
There's not an awful lot to install, and it doesn't take that long. But it would be nice to automate the setup using something like Boxen.