"Most importantly, Duet Display is the first app that actually turns your iPad into a second display I’d actually like to use. As someone who has tried Air Display and uninstalled it shortly afterward, frustrated, I can honestly say this is the only option that’s worth it."

Interesting, I tried Air Display and (another app) ages ago and used it off and on. It was "neat" and worked well as my Terminal window but a very poor stand for a monitor.

Looks like I'll be dusting off my iPad 2.