The app runs fantastically. I went through everything from signup to a booster draft with no problems, save one. That is the speed. This isn't much more an annoyance for casual players, but anyone playing in tournaments will soon see that the speed hit can be deadly. When you're running a clock, you need all the time you can get. Unfortunately, this make serious tournament play all but impossible. Other than that, though, it's perfect. :)
For reference, this was running on a MacBook Pro Intel Core Duo 2.0 GHz computer.