I'm mentoring some students on using various render engines, and since I'm using Corona more and more for personal work, I pushed them to test this one out. One of my students put a CoronaMapOutput on everything in the scene, including procedural maps (ie noise, cellular, etc) and when that is applied it virtually kills the entire scene. It takes forever to load and if you can get in max, it becomes so slow and sluggish it's unusable.
Why they did this, I'm not sure yet. I wouldn't think to do it that way, but leave it up to students to find new ways to use maps.
If it is a limitation of the CoronaMapOutput, perhaps a warning could appear before it kills your scene?