Hi
I just installed AE CC on a Dell T7600 Dual Quad Core 32 Thread, 64gb Ram Quadro K5000 Video card system. The reason I am saying this is it's not a slouch of a maching by any means.
First Bug
Opened up a project from AE CS6 scrubbed the timeline and bang crash, "AE has crashed do to classic render"
Click on the menu's at the top File, Edit Layer etc. You click and you have to wait 5 seconds for the menu to open up. This worked fine and very fast in AE CS6 what changed.
Multi Processing rendering in Ram Preview is worse than what it was in AE CS6. Their are numerous boards all over the web talking about how Multi Processing was broken in AE CS6 you would think they would of fixed it by AE CC. Went to do a ram preview using multi processor support and first it started saying it was saving my project (not sure why that was) Then my system tried rendering it and it was going so slow, All processors were being used but AE was only rendering one frame at a time. When I tried to stop it by pressing the esc keep like usual the system locked up solid. I had to end all processes through the taskbar to get access to my system again.
If Disk caching is used then the Multi processing won't even get past the first frame becasue it keeps using the cached files. What ever you have cached it keeps rendering right up to that point. Again this has been addressed as a huge issue with AE CS6 why is it still not fixed.
This is just what I found after using AE CC for 5min.
Hope it works better for everyone else.