I guess you have a FM receiver attached to your CI processor? In this case the FM receiver get's powered by the speech processor batteries making the battery lifetime shorter, that's a small drawback when using FM systems.
You're right, the sound quality with direct attached or integrated FM receivers is much better than coupling FM over the T-Coil. I think sound quality of inductive Neckloops is fine, but on the train platform you only hear the hum from the power lines picked up by the T-Coil :shock:.
For ITC...
Well, i'm very that happy that I've never regreted my choice. If you don't like to have your ear occluded all day, you may remove the acoustic amplification part and add the small hock. This can be done within seconds and then you have an OPUS2.
I actually wear the new DUET2, what other information are you looking for?
http://www.medel.at/english/30_Products/EAS/DUET-Audio-Processors/DUET2/index.php