We have been using this system for about 3 years, and put 32 grafts into a hive yesterday. We had one hive that absolutely refused to cooperate and removed the eggs from the cups after releasing the queen, but the other colonies we have used have been fine. Sometimes you have to allow the queen an extra 12 hours to lay up the frame, we use a magnifying glass to check the frame and find it easier to look for eggs looking through the back of the frame rather than looking into the cells from the front.
The reason we use the cupkit system is that we are both rubbish at grafting, and find we get a lot more grafts accepted this way. We are not needing the large no. of queens like B+., our last batch gave us enough for 12 mating nucs and 11 nuc hives, and some spares just in case some q cells did not hatch.
When we were grafting by hand into wax cups we were lucky to get 3 grafts accepted on a frame, and found it really frustrating. We started using the cupkit to simplify things and save our remaining sanity.