I have a similar issue on my machine, the behaviour is horrible! When I open a RAW picture and try to change the curve values, there's absolutely no change at all visible. When I try the same on a JPG picture, the same happens, although I might have to wait probably more than 2 minutes (once I was playing around a bit more without any effects), and then something happened to the picture. But the whole system is so awful slow!! This was not the case at all with 1.8.x version, also when I try the same with e.g. DXO Photolab, I don't have any issues or slow effects.
Any Information one might need to help me with this?
KR
TiRohn