The only thing I don't like about adjustable everything is it allows for 'play' in those parts and vibration and movement.
In a sense it could be good to have eveything adjustable but ive not yet found a need to adjust past the angles and settings ive created.
I have a few wheels and pedal sets and they all sit well on the wheel base angle ive made (10degrees) and pedal base..
Ive had some small girls and big blokes on the rigs too..