I have the full 70mm Termis fitted.
They do eradicate the bottom end lag reported by journos.
They are loud (deep loud) and its personal preference whether you like it or not. I do.
The look suits the bike IMO better than the standard pipes.
The screw in baffles do quieten it to a comparable level to the standard pipes at least below 5000rpm.
Is the full system worth it? Well as far as I am concerned, I am a Ducati owner (read Hedonist) not an economist - so Yes.
Just my opinion -helpful to some, thought provoking for others. Possiby, infuriating for the few - but hey.