It is too early to tell if making the change was a mistake or not. However, I am inclined to believe that it was not a mistake because if he gets used to the new motion it will make him a better QB in the long run. I am not concerned about this year because he has a lot of stuff to work through with the change and still getting used to playing football again, learning reads and getting used to the speed of the pro game. I think the rust was much deeper than many believed and he is still working it off along with the other stuff.
However, next year will tell the tale for Henson. If he is ever going to make it as a QB it will show next TC. For now I have confidence in Romo to back up Bledsoe for this year and expect it to be a dogfight between him and Henson in 2006 with the winner likely being the QB of our future (our future being after Parcells retires).