Is it expected to have visual glitches while constantly moving one window from a retina monitor to a non-retina one?
If I can direct your attention to this thread on the apple support forums

https://discussions.apple.com/thread/5547471?start=0&amp;tstart=0

There seem to be issues like this across many different platforms and in many different circumstances. Having read every post on this issue in the forum linked I'd have to say that the energy efficiency softwares and firmwares between all of the different devices result in random and irritating UI lag. Not really a solution though.