All valid points. If it is what it seems like, it really presents a formidable challenge for many of us. Renders that take 20 seconds instead of an hour, instant feedback on scenes and materials, and simple setup and transfer from something like Revit and Archicad. At a certain level of quality it is not a question of whether Lumion produces better results than Vray or Corona, it is whether it is good enough. How many of us can honestly say they can improve on the picture above of Paris?
From what I have seen I think it is more than the render equivalent of Sketchup, which although it undoubtedly has a strong following, probably never became the killer product many expected. Sketchup falls between categories, which sometimes can be a blessing but sometimes a curse for a product. It is not strong enough to compete with 3ds Max for a full-time visualizer, but at the same time not CAD and parametric enough to replace something like Archicad or Revit. Hence, where Sketchup has become a parallel track, products like Lumion aims to replace the step where the architect needs a solid render for presentation or review, i.e. a huge portion of the current architectural visualization market.
I know quite a few architects, and if a solutions is in any way messy they will stay away, but if there is a realistic opportunity to control renderings by themselves they will immediately take it.