Ok I am going to throw this out there as to why this works. The reason why this works is because Tony Parker, unlike Miller, is used to playing off the ball at times when Manu Ginobili is in the game. When the Spurs have Ginobili in the game handling the ball, it is virtually just like when Roy is handling the ball here in Portland. The other side of the coin being, I have always felt one of the problems with Roy and Miller is the fact that Roy did not want to defer to Miller, because the fact is Miller is not as good as Roy, and it is hard to defer to players that are not as good as you are. With Parker having multiple championship rings and all star appearances, Roy really can't do that. The other thing Parker brings is speed. For all the open court savy Miller has, he is not a very fast guard. Speed creates problems, and those problems are not your teams problems.
As for Mathews, I think there are a lot of people who are uncomfortable with the trade because they haven't seen a lot of him. I have seen enough to be very comfortable with the trade. By end of last year, I was openly wondering while watching some of Utah's games how we could get that guy, and how lucky Utah was to move Ronnie Brewer and end up with a good upgrade by doing so.