First, let's be clear. I'm a satisficer, not a maximizer. All cars are compromises, and this is expecially true at the lower end of the price spectrum. I'm 6'2" and, ahem, let's just say over 300 pounds at the present time. I can get in and out of this car with no problem. It runs like a charm, turns on a dime, the steering and braking are silky smooth and I've still got a quarter of a tank left with the odometer at 325+ miles, so I'm heading for 40+ mpg on the first tank. Yes, the seats could be better, maybe Toyota will fix them, maybe not. The cup holders are neat - you can send the air around them - or use the AC to cool your drink. Nothing's perfect, but the Yaris is awfully good.
Nice big doors, easy entrance/exit for tall people + excellent visibility when driving. Wonderful almost magical turning radius makes parking in crowded parking lots almost fun. Lots of places to stash assorted stuff. Handles speed humps with aplomb.
Shift lever difficult to set in dark, the seats indeed need a bit more thigh support or, at least with the power pack maybe Toyota could throw in a bottom angle adjustment on the drivers seat at least so taller drivers could get the front of the seat up under their thighs.