I just got the game and played it for the first time.
There is one thing that bugged me a bit.
The fact that all houses can muster the same amount of pieces (knight, SE, footman, ship)
I think it would have been a bit more interesting if it would have been different between each house.
Greyjoy having more ships units to muster.
Starks having more Knights.
I'm not sure about the balance between the houses with the unit but I'm sure better men than me can think of the right balance and making it more fun that way.