Old thread, but I will share my recent experience. I'm 6'4" with relatively short legs. Just sat in a Gen5, and I'm disappointed to say it a "no go" for me. The dash is the least of my problems. When I recline the seat so my head doesn't hit the roof, my head is slightly behind the b-pillar so my view to left is blocked. I can get in and out OK, but i have to bend exactly one way to get out without scraping my head on the door frame. This gets old fast. I bought my gen4 specifically because it was the smallest car I could comfortably fit in. I don't really fit in any other Toyota that I've tried (no Corolla, Camry, Rav4 and now Prius). Oh well. The Korean cars supposedly have better headroom - at least according to the official dimensions - but that doesn't always map to real life for me. At least i still fit in Volvos.
I am 64 years old myself and currently 1.79 m tall. When the Prius 5 first came onto the market, I read many negative comments about it. They were said to be far too small, the driver's display unreadable, the entry difficult, and lacked headroom, etc. But I am still very satisfied with my Prius 5. In every car, I slide the steering wheel all the way forward and not to a high position. The view of the display is then perfect, and I am never bothered by things like a small head-up screen. My Prius also has the panoramic roof, and with the seat positioned slightly higher than the passenger seat, there is still about 12 cm of headroom left. In very high outside temperatures, if I roll the sun blinds closed, there is still 8 cm of headroom left. In an Audi A5, BMW 3 Series, Alfa Giullia Volvo V60, Mercedes CLA, or C-Class, I have to lower my seat by about 5 to 8 cm, otherwise my head hits the roof. However, because of that low seat, I do have trouble getting out.