I was at the Berlin clinic for a consultation last fall. It was a bit hard to really get good info there, but they said their success rate in glottoplasty is 30% - measured exclusively by the satisfaction of the patients. 30% said it was worse and the rest was ok, not much change. Now for one thing, thats a horrible rate and another reason to go to Yeson instead, but what puzzled me was how this can be - if you tie up the vocal chords, the lowest possible pitch HAS to increase unless you really harm something else. The Prof there hinted towards that the pitch increase actually really doe shappen. The old studies of the clinic also show that there is almost always a significant increase in pitch (the Gross et al paper). So adding the experiences from the people in this forum and in the Yeson group on facebook, my conclusion was that besides the possibility of harming the voice due to the surgery - which certainy is part of why the stats in Berlin are so bad - if the voice gets weak, breathy, hoarse, people will of course describe it as unsatisfactory - a main reason why people are not satisfied with the voice may well be the expectations they had about it.
Many go there with the expectation that their boomy bass male voice will be made into a female sounding voice , which usually does not happen with surgery alone, it always takes additional training and they dont like that or see it as a flaw of the surgery. Another group seems to be the ones who did voice training, have a good feminine voice and expect somehow that the voice gets even more feminine with surgery, which also does not happen as it will just make using the feminine voice easier. The ones most satisfied seem to be the ones who had a feminine trained voice before, but had a hard time to keep it up, strained while doing so, were sad that it still had a male edge to it and that they could still accidentially drop down from it - in that case surgery helped to take away the strain, made it more natural and removed some of the male edge to it, making it more naturally feminine.
So I would never dismiss a concern or dissatisfaction of someone with a voice after VFS, but I would always look into what really happened, what were the expectations, what changed really and how does it relate to the results that can realistically be expected and the expectations of the patient.
That said, a total lack of change in pitch (especially the lowest possible pitch) or easiness to reach a feminine pitch when speaking after 3 months would worry me too. If the suture holds, which can be easily checked at a ENT with an endoscope, the only reason I can imagine is swelling of the chords which keeps the pitch low until it is gone, accordiung to Yeson this seems to take up to 6-12 months...