I've not had much to do with the hybrid and ion range gts,fitted a few and always carried out a pre install radio survey.
I seem to remember we were always aiming for a reading of four or above,eventhough the threshold reading of three would suffice,( please correct me if i'am wrong :),
Had a couple of the hybrid panels suffer from RF signal drop out,but that was mostly because of internal alterations(stud walling) etc.
Then of course these large panel plasma tv's became all the rage, found these, especially if they were wall mounted caused issues described in this ion post.Must be the high voltages that play havoc with the signal, still got the survey paperwork and the scanny 790r + 703 four chan tucked away in a safe dry place.
But yes you are correct in saying it's quite an expensive piece of kit, and an essential kit if you install and maintain the ions :) :).
e manno
September 2012