Like smithsax, I took all week over this puzzle and it's the first time for a while that my solving of the next week's puzzle has had to wait just a bit until I'd finished the one before! That's largely because of all the cold solving that was needed. I got there in the end, though, and this thread resolved just a couple of parsing queries I'd had.
I sort of agree with ALL the comments, positive and negative! It's a mixed bag of a puzzle for me. Hard, but tractable. Tedious in places, and delightful in others. Brilliant in its conception and execution, but spoiled by a few glitches that could, I think, have quite easily have been tidied up.
There was a lot that could put people off this puzzle. The amount of cold solving required is daunting, and the clues aren't particularly easy at that! I got to about thirty before starting grid entry, and I see that others have commented similarly. I then started doing some trial-and-error guesswork, making some outrageous assumptions, to start getting words into the grid so that the emerging messages could help me solve the remaining clues. It all worked out, though, thankfully. Then I nearly threw in the towel at the replacement phase because that just sounded so tedious, but I'm glad I persevered because it wasn't as bad as it seemed it might be and as the final shape emerged it was just awe-inspiring. Utterly brilliant.
I do think it's a shame that the archaic or dialect markers were missing from some clues, others used a bit of a strained definition -- I do realise that the endgame put some pretty aggressive requirements on the clues, but some of the problems could still have been solved. For example, unless I've misread something the last printed clue actually mismatches its solution in part-of-speech, which is something I don't expect in Listener crosswords and could be easily fixed without affecting the endgame at all. Given the amount of cold solving that was needed, just a little more care to tidy up that initial solving experience would have put the crown onto an already very very clever puzzle. I did enjoy it, on the whole, greatly though, so thank you Twin and thank you to everyone who posted comments and encouragement that urged a doubting me to continue to the end of it!