In reply to Stone_donkey:
I upgraded a few weeks ago from LR 5 to 6 having been waiting for the version 7 which is not as you know now happening.
No problems with upgrade itself direct from Adobe website or any noted slower speed (4 yr old pc) except on initial start up of program - on my pc it is maybe up to 20 sec slower to load. Once loaded up it seems quicker overall however even when multi tasking from my uses so far. The start up could be of course just my machine spec (or window 10 updates which I know on my machine demands higher pc resources for too long) rather than LR6 being slower to start or just a perception given that it displays a “splash” for a bit which draws your attention more than LR5 startup.
It was a worthwhile upgrade for me as I wanted to stay with LR stand-alone meantime, but I needed a min of version 6 to be able to support reading raw files direct from my camera rather than having to use an intermediary program or conversion to DNG.
I’m happy and no regrets with choosing LR 6. Hope that is of some help.