We are getting near a time where we will be able to not only replace body parts for medical reasons as we see today, but possibly even do so for aesthetic reasons (Body Modification). It is difficult to deny that times are changing. Which body part would you want to enhance with a robotic system?
I sure would enjoy having super-human vision and data storage like in Jonny Mnemonic 
In terms of functionality, all of the above. There is a certain appeal to having perks/improvements beyond human limitations.
I would do it in a heart beat! I have been disabled since age 18, my first year of college. Sometimes it is soo frustrating I can hardly stand it! If a robotic system could make me function like a normal person, I would be so happy!
Beyond that, I would love to have the ability to learn and apply knowledge super fast as well as be faster and stronger physically.
When Neo downloaded the martial arts skills in the Matrix, that was cool!