The problem causes start up issues and, potentially, kernel panic and occurs “”when running certain apps that capture video” according to Apple.
We installed the update this morning on a recent MacBook Pro connected to a Cinema Display. The installation went smoothly although during the post-installation restart our screen did stay black for a little longer than usual and it took a few moments longer than normal for the system to be usable. However, our initial feeling is that it hasn’t introduced problems.
Developers will also see an update for the 10.10.4 seed come through Software Update.
According to sources, the seed note doesn’t highlight any specific changes or issues that addressed in the update. Now that Yosemite has been around for close to a year, it has reached a solid level of stability, notwithstanding some of the challenges faced by users adapting to the changes Photos has pushed out.