I just wanted to draw attention to a seat mod that was first posted at PriusChat earlier this year:
Click Me
To summarize, the seat is connected to the rails at the front and at the rear. It is possible to modify (cut, grind, and drill) the rear mounting point to lower it up to about an inch. The front stays at the same level, so it becomes a bit more bucket-like. There are pics of the process in the referenced thread.
Long story short, I spent about 6 hours on it last weekend and I'm thrilled. The mod does two things to address my 6'1"+ frame. First, my head is no longer right up near the roof. I no longer have to duck to see around the rear view mirror in a big right-hander, nor do I have to duck to see a traffic light that's closer than 1/4 mile away.
The other benefit is that I actually have thigh support! The stock seating position is garbage, resembling the bench in my dad's 20 year old plow truck. Even after I "got used to it" it drove me nuts. Now it's great. Still not Benz or Volvo comfortable, but easily good enough to live with.
The only down-side from an ergonomic standpoint is that reclining the entire seat means that the back can't tilt forward quite as far as it used to. Not a problem for me, but it would be an issue for somebody with shorter arms. I also think that it would be possible, in theory, to go too far and put too much pressure on the thighs. Again, not a problem for my long legs but everybody is different.