I normally don't carry on my bike since I can't take a gun with me to work, but if I'm on a road trip I may or may not carry as it depends on the states I visit.
But when I do carry, I have a comfortable shoulder rig I barely notice while riding, and I carry a full size Glock. Never gave much thought to having to draw my gun while on the bike as that would be impractical at best trying to get through my jacket with gloves, etc. My thoughts always were that to have it is better than not having it if the need arises, such as during stops. Even when I'm in a "cage" (car), I've never been too concerned with needing to protect myself while in the car. Guess I always just thought the need would most likely be greater while away from the car. I think the same goes for a motorcycle, albeit there are obvious differences, especially while stopping at a light for example.
Then there's the whole "accident vs. protection-with-a-gun" thing. Both events are rather unlikely, with a crash having a little higher probability than a "bike-jacking," for example. Guess I just think if I need to worry about getting hurt by the gun in a crash instead of everything else trying to do damage to me in that instance, I'd better rethink riding at all.
I'd rather have the gun than not have it. Just wish I could come up with an easy solution to the "taking off the jacket in public" part.