Auto Layout is making my life difficult. In theory, it was going to be really useful when I switched, but I seem to fight it all of the time.
I\'ve made a demo proje
I just solved my problem using the multiplier feature. I'm not sure it works for all cases, but for me it worked perfectly. I'm on Xcode 6.3 FYI.
What I ended up doing was:
1) First getting my buttons positioned on a 320px width screen distributed the way I wanted it to look on a 320px device.

2) Then I added a leading Space constraint to superview on all of my buttons.

3) Then I modified the properties of the leading space so that the constant was 0 and the multiplier is the x offset divided by width of the screen (e.g. my first button was 8px from left edge so I set my multiplier to 8/320)
4) Then the important step here is to change the second Item in the constraint relation to be the superview.Trailing instead of superview.leading. This is key because superview.Leading is 0 and trailing in my case is 320, so 8/320 is 8 px on a 320px device, then when the superview's width changes to 640 or whatever, the views all move at a ratio relative to width of the 320px screen size. The math here is much simpler to understand.
