I have not stayed in an IV, but really think, in fact know, they are not for me. I enjoy time on my 'real' balcony rather than fighting for a lounger on the pool deck and believe the lack of the feeling of being outside would be missing with an IV.
I would hate to plan a cruise and look forward to it for months, only to be disappointed. Maybe if I had several cruises a year I would book an IV as a tester and decide then. But, as I save for and look forward to my cruise for many months, or years in advance I think it is not something I would chance.
Yes, there are lots of ships to choose from. I have tried other cruise lines but really love Celebrity and as I choose my trips for itinerary my search for a cruise I want in a regular balcony cabin is becoming more difficult. I am all for innovation but I think new ships should include both types of balcony. That would satisfy both sides of the argument.