Metal, as introduced by Apple last year for the iOS platform, is an API that should give better performance from the CPU and GPU on Apple's computers. They released it first on mobile with iOS 8 last year. The company touted that this would dramatically increase game performance, leading the prettier and more complex graphics. It seems to have been pretty successful.
At WWDC 2015, Apple announced that they would release the same for Macs with the new version of their operating system, OS X. The current version is OS X Yosemite. On September 9, Apple will probably give us more information on OS X El Capitan, which is going to include Metal. A download date should be known.
Now, the reason I'm bringing this up is that Metal is advertised as being able to increase performance in, amongst other, the Adobe CC suite of programs. And we're talking pretty noticeable boosts here. Being a GPU oriented update, video people using Premiere Pro and After Effects should see the biggest increase. However, Photoshop and the like will go up in speed as well. As soon as I can get my hands on it, I will do a comparison of the speed it takes to output files and apply heavy filters in Photoshop using my MacBook the see whether or not it is really speedier.
I hope I will conclude with positive numbers. Who doesn't like to have free speed upgrades?