Some implements are poorly designed, and you can't get the big hook of the top of the quick hitch into them.
Some implements have different spacing between the lower and upper pin holes. Again this is just bad design.
Look over your implements so that all work. THRN it is great deal.
Some implements like a post hole digger or a backhoe cannot use a quick hitch because of their design. If you are switching to one of these type of implements often the quick hitch might be in the way more than it helps, as you always take it off and on....
If you use a lot of pto stuff, the quick hitch adds a couple inches to the length, some implements this makes the pto too short, or it changes its angle.
Some implements are very heavy, like a round bale mover with a bale, if you lift very heavy loads near the Lin
MIT of your tractor, the quick hitch moves the weight back a few inches, and will make the front end even lighter, or the tractor might not now lift the load.
If you use the hitch on the tractor a lot, the quick hitch is kinda hanging there in the way, bit of a bother.
Yea a long list of negatives, but generally those aren't big problems, the quick hitch generally works out well. Just pointing out the stuff to look out for.