... LR6 runs faster in the develop module due to GPU support...
Glad it works for you, Hans.
My experience is the opposite: frequent crashes, beachball spinning, long time delay between a brush and its effect, freakish behavior (like when you press "L" it blackens the whole screen, not just the outside of the image - but only sometimes). If I did a perspective correction, and then moved to something else, say brushes, every time it refreshes the brush action, the images jitters as it goes into pre-perspective correction first and then settles. Etc., etc. Feels more like a beta version than a final release. I am on (thin) iMac 27", 24 GB memory, Yosemite 10.10.3