Never use the transmission parking brake when transporting, you can cause serious mechnical problems by doing so. They flat say in the owners manual that this is a no-no.
I don't know about everyone else but I would only park and get out of or off my ride on a fairly level spot unless it was an emergency then I think I would look for something to block my tires. And to answer your thought I ride in Idaho, and we are not exactly flat around here.
Just my two cents.