I dislike the fact that there are compatibility issues. I'm too cheap to go purchase new equipment just so that it would be compatible with a QH.
As Jay says above, all of the issues with bushings, pins, hooks, adaptors . . .
I despise the fact that most cat 1 QHs are not really cat 1. The only 1 is the SpeeCo E-hitch, I believe.
I added hydraulic T&T and this has made implement hook ups uneventful. Having individual control of the 3 points of the 3P makes life so much easier. And, that transfers over to usability of the implement while in operation.