First off: Brilliant mod Meph, very appreciated the work you have put in.
I am on my 3rd Masterwork fort now, and I have run into the guild joining problem some others have reported. My first fort to do so.
Appropriate dorf grabs some gold, runs to the guildhall, I get the msg a dorf has joined a guild and there is a puff of smoke but that's the end of it - they run off to do whatever and gold is consumed. No waiting around for a week like normal. On one occasion, a dorf ran about 18 squares away from the guildhall then suddenly got the transformation, as if it was delayed. On all other occasions the transformation took place immediately, or not at all, even waiting and trying again with the same dwarf a week or a month later.
This is not happening to all my dwarves though. 3 of my 5 miners joined ok and on the first attempt, the other 2 do not as described above and continue to be stubborn. Unfortunately my best armour smith and weapon smith do not join the smiths guild. The one and only beast warden to try to get his guild robe on, joined no problem. 2 farmers out of 5 also do not join the guild. I have only tried one military transformation so far and that worked fine (legion). DT shows the dorfs that still do not join a guild properly are still "Dwarf" caste.
I don't think there is anything special going on in my fort that might be relevant. Things are ticking over normally otherwise.