I have an iphone 4 16 gb , and there is not much of a change in disk space for me ! But there is a significant change in the way things run ! Everything except the camera is slower by 1,5 seconds average !! And you have to do a lot of settings alchemys to change that a little ! And some 3d games that used to play super smoothly with iOS 6 now are on slow motion and it's super annoying ! (Example some endless run games like monsters univ. Stuck all the time and. Any be played ! ) the typing and the scrolling are slower too ! Only after following some advice on what to turn off on settings I managed to make the 3d games play well ! They really did improve ! But the scrolling and the calls even are slower ! Ex. I click to call a contact and the call screen appears after 2 seconds I can't even close the call fast if I regret it !!!! So WAIT AND USE IOS 6 !!! If ps : I have 40% ram free when doing nothing and my friend with iOS 6 has 63 % I also must say that I have more installed apps than her but still ...