Hi, I am a Windows user who is seriously considering switching to Macs. I visited my local Apple Store and I found some curious things happening when playing HD video and I hope someone can shed some light on this because I can't find anything about this online. Apparently, every computer in the store has a short trailer of "Oz, the great and the powerful" on its disk.I tried to play it full screen on two machines: 1) a 27" i5 iMac 2) an i7 Mac Mini connected to an Apple thunderbolt display The iMac was performing very poorly. The video was constantly stuttering quite noticeably and I believe anybody would say it was not smooth. The Mac Mini wasn't perfect, but it was a lot better ans perhaps some may not notice the stutter. Just to rule some things out, I downloaded VLC on the iMac and there was no change compared to QuickTime. I must say I am a bit surprised because I thought in 2014 any modern computer would be capable of handling HD content without particular problems. However, I am even more surprised by the lack of information on the internet on this subject. The 27" iMac has the most gorgeous screen I ever laid my eyes on and I am sure millions of people must have bought it and watched HD movies on it. How is it possible that no one is complaining on the web? Does anyone have any experience to share on this subject? Thanks!