I love Fallout Shelter. It is a great little game (I have named my dwellers after family and friends and that adds a new dimension of fun). But I have a suggestion that would make playing the game so much easier. If you have noticed that if you zoom out all the way the vault goes from 3d to a flat 2d, at which time it runs a lot more smoothly for those of us on iPhone 5s. The problem is that because it is leggy on my older phone, a lot of the time trying to zoom out causes me to inadvertently move dwellers to other rooms or select stuff I don't mean to.
Solution: put a small button in the bottom right corner that if you hit it it backs you out to max distance and centers the vault on your screen.
I love you Bethesda!!!