I can report a real world test with a full spec new Mac Pro, I got 19 layers of 1920x1080 @ 25fps playing back seamlessly (encoded as AIC using Cat's built in conversion). This was on 10.9.2 and I had a couple of crashes during programming but only until I converted the media. Media played from the Mac Pro's boot drive (1TB SSD). What else? All on one mix, many of the layers in colour fx 85, many using visual fx 204...

In short. Wow.

T.