The version of the preamble that the test-solvers passed by ended up being changed rather dramatically, based on my records, so maybe their opinion is no longer as relevant on that point at least. I think the consensus at the time of test-solving was "tough, but doable".
The preamble that made it to the published version is mostly down to the IQ team (although before it looks like I'm washing my hands after all, I did OK their changes).
I have to say that while I'm apologetic it's pointless to deny that it's been frustrating to read the negative comments. I hope solvers enjoyed the clues, at least; and, while the execution may not have been perfect, I hope they agree that the idea was worth writing an IQ about.