You and me both, friend. I hate reachability with a passion, for the simple fact that when I got my first iPhone I had never heard of the feature, and it's literally taken me 1 year to understand why sometimes my screen would look weird. No amount of Googling or searching the settings helped, until someone mentioned the magic keyword "Reachability". Which then was easy to disable.

So it might be a cool feature, but if you don't know about it you'll go mad trying to understand what is wrong with your phone. And it's not like Apple is good at teaching users about power user gestures. I still feel I'm not using my iPhone at its full capacity yet.