I agree the swivel is nice, but I haven't had a big issue with the fixed couplers, so while I would rather have the feature, it's not a deal killer. As far as mating up with the existing couplers, this one sample I have mates up perfectly with all the things I've tried it with. The couplers activate very easily and don't separate until I want them to.
I suspect much of the complaints may stem from poor quality control as from design.