Question came up today about using Auto Layout but ensuring pixel boundaries.  Apple writes:

The solution is to make sure that your drawing aligns on pixel boundaries rather than relying on points. You might also consider using Auto Layout for constraint-based, pixel-precise layout that works well for dynamic window changes. For more details, see Cocoa Auto Layout Guide.

and in the Auto Layout release notes:

For resolution independence, this system allows for pixel-perfect layout at non integral scale factors for interfaces designed in Interface Builder. Neither was previously possible.