It was fine until DP7 (at least from DP4~6 were fine to me). Sometimes the whole Screen freezes and you cannot even move your mouse cursor. At the very first I thought it was something wrong with my mouse connection, perhaps bluetooth connection failed and thats why I couldn't move it. But it's not. I watched a movie and the movie itself freezes for few seconds every 5 to 10 minutes and during this time only sound works. So Im 100% sure that this was a bug. And I shot a bug report to apple.