Look at the motherfucking installer for one tiny example. One keyfumble or one return too many and you are FUCKED, have to start over. Haven't you fucking ASSHOLES heard of "go back"? How far up your own ass do you have to be to code such a DEEPLY SHITTY INSTALLER that it won't even allow the user to go back and change that important N to a Y? You don't even have to keep state just store important choices as variables and allow us to change variables at each prompt.
About a week ago, I was trying to upgrade my dual boot laptop to 3.7. I had to run the installer about 20 times to figure out my problem and correct it. In the process, I learned more about fdisk and disklabel than I had ever needed to before, and I count that as a good thing. It took no more than about 5 minutes each time to run the installer from scratch to completion in each case. Typing Ctrl-C and then "install" when you make a mistake isn't that difficult.
-- Scott Plumlee PGP Public key: http://plumlee.org/pgp/