I think he's definitely one of the current top tier drivers in F1/recent times. HOWEVER.. (Before i get attacked... :O ) As has been show with the Mclaren he needs a car that suits his style to be at his very quickest. He doesn't appear to be one of those top tier drivers that can adjust his style to suit the car's characteristics and still be quick.
This is a decent explanation of what seems to be going on with Danny R.
This is a decent explanation of what seems to be going on with Danny R.