This is a great thread and it really has got me thinking.
My lady friend does not express much interest in riding her own bike on the street but does want to learn to ride a dirt bike. That's fine with me, I feel safer having her with me and we both enjoy the day trips out to the coast and out to eat.
On smaller bikes I have had you do have to change the way you accelerate, shift, brake, corner, etc... But on my Bandit 1200 the bike couldn't give a shit whether she's riding pillion or not.
Sometimes I ride to get away from it all by myself, but other times it's nice to have the lady friend along to share the experience.