In the new \"Xcode 6\" the ability to change the center of measure of a button is missing.
In Xcode 5: http://imgur.com/jWHJp4v
Xcode 6: http://imgur.com/rsNayVZ
If you are using auto layout then this two will help you place you control in center for all the view different size of devices.
simple:
http://technet.weblineindia.com/mobile/using-auto-layout-in-xcode-6-for-universal-ios-app-development/
Advance:
http://www.youtube.com/watch?v=G53PuA_TlXk&feature=youtu.be&list=UUtc1Jt_UTPsXpAGtvlr0nUQ
Apple has removed this feature as there are 4 different size of devices only for iphone and it would be difficult to set frame for all controller and will increase the length of code and will become a tedious task as it check's the size of device and then set frame so in XCode 6.0.1 we need to use auto layout + size class and prepare our view based on the constraints set in storyboard or Xib.
Hope the above link's will help in solving your problem.