Short and sweet: You can dash (bursts of acceleration for a limited period of time), accelerate by diving and fly at fast/slow speeds (similar to run/walk like Raze said).
Well, I'm wondering how can player in dragon form attack ground enemies? I assume dragon can burn them by his fire as well as he can burn flying monsters, but has he some other attack skills (we only know he wont have ability to burn wooden buildings
)? For example: can dragon lacerate ground enemies by his claws/jaws or knock them down by flying too low - dragon flying just above horse can put down a horseman (and scare horse to death), dragon flying just above wall castellation can knock down warriors from a wall.
I really like to imagine these situation... king of fire monsters dive from a sky and cause havoc on the walls of some fortress only by his wings....