The heated seat on my K1300GT doesn't get very warm, after around 20 minutes it is quite enough to feel heat, however unlike the seats in the car, there is no sensation of being burning hot.
Some months ago the dealer tested it (measuring warm - up time and temperature) and pronounced it fine.
He did say (quite sensibly I think) that in heavy motorcycle clothing, nothing is going to feel very hot, and it also loses lots of its heat to the air rushing by.