Ron, I just took delivery of a IV. I've had it for two days...so far, so good! FYI - I got the IV because I wanted: (1) sunroof and (2) solar cooling system. Can you get heated seats in the III? I don't know, but I think they are nice to have...
That coating would probably be destroyed by the windshield wipers when you use it over and over again.
I have a 2010 Prius IV and i am more than happy with it. I had it only for less than 2 months, but i cannot resist driving it. Except for the Nav, all the other features are worth the price. This is my first Prius and so cannot comment on the side windows aspect of this post when compared to the GenII. But i dont have any issues with visibility on my Prius.