I agree about the hi res GUI, although I'm not really sure what touches you are referring to. I also think it doesn't need to be quite that big. Maybe I would change my mind on that if I played the game. Overall I think it's a very good change though.
I suspect holding down the mouse and having the slash direction would be a good way to allow the user to easily perform several different attacks. I don't know about anybody else, but I always have a hard time with those games where you have to do <- + v + -> + jump + attack in order to do a special move.