First of all, thank you Steinberg.net for getting the high resolution version pushed out with Cubase 8.5! Looks great.
I am on a brand new late 2015 iMac 5k with top specs (4.0 ghz i7 skylake, 40GB RAM, 1 TB SSD, M395X graphics).
When zooming in and out of the timeline, the gui gets laggy. This is especially evident when looking at audio files. It could feel a lot smoother.
I don’t think this is my computers fault (as CPU and GPU usage are low).