The innerclock plug in is going to be delayed with everything else in the system via delay compensation. Its accurate. Most everything has automatic delay compensation and while yes things can go wrong here with plug ins not reporting correctly or something that isnt a problem with any of these systems we are talking about. And you would still have this problem working with usb midi.
Im confused as to your argument as of course midi clock over usb is sloppy as all hell. I thought you were referring to your audio being jitttery. Thats what these products solve - sloppy usb/firewire midi. They solve it by using a audio signal, something that daws are very good at keeping in sync.
Have you used one of these systems?