I dont see any need to be too careful with Corona, its currently free and very easy to use, so where's the risk? Its not like you need to spend an age learning it, just load in your HDR and hit render! I've used it on some arch scenes and now on an animation scene, (see attached). In Mental Ray this scene takes an age just to FG but here Corona is waaay faster, the results are also far better out of the box. Of course its not ready for larger studio workflows yet but for smaller ones and freelancers, why not. Corona works like a render engine should.