Nevermind winning winning a title, but when was the last time an uptempo running style made it deep in the playoffs? Half court basketball wins in the NBA playoffs. I never understood people's desire to have a young uptempo team. They dont win in this lleague.
I think what you want is up-tempo _offense_ but half-court _defense_.
The highest percentage shots happen in transition, before a defense is set. You want to get the ball down the court quickly and attack the hoop with a high-percentage shot. The more efficient you are at putting the ball in the hoop on a possession, the more often your opponent has to bring the ball in from out of bounds - this in turn helps you get back on defense so that you can force _them_ to play half-court and thus hopefully take a lower-percentage outside shot.
All that said, in the playoffs, opposing teams often are much better and harder to run on and you simply _half_ to be able to play half court offense effectively because they will force you to. When the games get close and the clock is ticking, that is how the game is played.
So while the desire is strong for being able to run on offense and there's nothing wrong with that, nick is correct that ultimately you still _have_ to be effective playing half court ball.