The subject line of this thread finally applies to me, what a relief to have it at last, along with my US passport and other supporting documents.
It took less than two weeks from the date of my citizenship ceremony to have that lovely UK passport finally in my hands.
Here is my timeline:
7 March: Naturalised at Citizenship Ceremony
9 March: Applied for UK passport using Post Office Check & Send Service
(Somewhere in this date range, delivery of my supporting docs was attempted, but I was not at home.)
17 March: Received passport interview invitation letter
18 March: Attended passport interview, received supporting docs delivery attempt letter, dated 17 March, from SMS
19 March: Booked redelivery of supporting docs for the next day
20 March: Received UK passport & supporting docs in the same delivery