Does anybody have any idea how well the iMac 27inch 5K Retina display 3.4ghz handles 4K video editing?

I recently bought the iMac with the Radeon Pro 580, and it's doing just fine with 4K video, although I've not pushed it yet. I don't think the 580 is too different from the 570. It does have 8GB VRAM though.

I only have 8GB ram, but will be buying a couple of extra modules soon...... another thing, I use FCPX, not PPCC.

Thanks for the points! Yes, it's been fine and I'm importing 4K as is, i.e. not optimising or creating proxy.

I did hear that an i7 would help video as it multi-threads or something, but I have the standard i5 and it's doing great, so far.

Why not post on one of the video forums such as the Final Cut Pro forum or a Premiere Pro forum?

Final Cut Pro X