Hi, I have an iMac 27" that I'm generally happy with. The config is the following: • 3,5 GHz Quad-Core Intel Core i7, Turbo Boost ´ 3,9 GHz • 16 GB 1600 MHz DDR3 SDRAM - 2 x 8 GB • 512 GB SSD • NVIDIA GeForce GTX 780M w/ 4 GB GDDR5 At times, this computer which is brand new turns out to be extremely slow. It can be everything frmo Safari freezing and refusing to shut down, to the App Store not responding and me opening the Force Quit Applications feature; and then that one freezes too.. It's sort of annoying when you've shelled out €3000 for this computer.. Any ideas? I'm running Yosemite if that's relevant?