Sheet film was a huge disappointment to me; 4x5 and 5x7 was a total waste of time and money. I had to go back to medium format to save myself from being too technical and thinking too much. Funny how different we all are!
To counter the question of poor camera design, I think that the camera that allows presents the least amount of barriers between subject matter and the photographer's senses is the best one, and the worst one is a camera that completely clutters the work flow with considerations. The more intuitive it is to use, the better it is, and the more you have to think, the more it sucks.
But then again, practice makes perfect, so maybe with enough use any camera can be easy enough to shoot with... I think consistency matters, and something that seemed counter-intuitive to begin with can be a very good solution. For example, I love shooting my Hasselblad hand held. I would not have thought it when I got it, but now it's as obvious as day that we get along very well working together.