works well, stability issues on rMBP

Air Display is pretty amazing and tries to solve a hard problem. It does a decent job. Using an iMac as a secondary display is good as long as you dont mind some lag. The biggest issue for me is that it is not super stable. On my new retina mac book pro, air display causes the machine to lock up a few times a week or not come out of sleep correctly. Theses problems started when I bought Air Display and stopped when I uninstalled it in favor of Synergy (which is solving a slightly different problem, but in my case works well since I can use easily use an old iMac along side my new notebook) it isnt quite as nice since you cant drag windows across displays. Overall, Air Display is pretty good, and Id imagine if using an iPad it would be fantastic.

Ryan Horrisberger about Air Display®