So, I finally got the shout which tames the dragons and allows you to ride them but, when you do, you have no directional control over them AT ALL! You just fly around in circles over your current location. What a HUGE let-down! :-(
Think the deal is because Cities exist in their own world-space and if you don't enter thru the gates (and on PC use no clipping code) you will see that the cities have just the very basic meshes (shapes with just enough texture so the view from outside at ground level looks good). So if you could control flight and fly straight toward the cities or over them what you would see is really nasty looking graphics. Because you are not meant to see the cities without going into the world-space.
This is why Bethesda didn't put that in there. BUT I can almost guarantee that once it comes out on PC a mod will be created to fix this (at least the controlling the dragon's flight part). Also with the Open Cities mod the city graphics should work as well (earlier comment).
I'm hoping there is some changes made it this. Perhaps something as simple as a 'go that way' command. I was sooooo disappointed with the dragon riding I've hardly played the Dragonborn DLC at all. Additionally riding a dragon can and will crash your game eventually.
"Fix this" it's how they meant it to be. It doesn't need fixing. And how would you control the dragon? Your not making them your thrall, your making them willing to help you in a battle.
If you can ride the dragon, it is expected that you will be able to have full control over it. Otherwise, what is the damn point of adding this feature to the game...?