Thanks everyone for generously sharing your knowledge.
I shall be travelling late November 2013 - well before the UA change in seating. From the pictures (fantastic - many, many thanks), the level of privacy between seats favours QF. And I am worried by the gymnastics that would be required in the UA configuration for the window passenger to step over the foot of the aisle seat when it was in the bed configuration. Not to mention the absence of storage space for the window passenger in the UA configuration - which would necessitate clambering over the aisle passenger to access the overhead bins.
The prices that I have been quoted are exactly in the range indicated (ex-taxes) - i.e., low $8K for QF and mid $6K for UA.
I have a 3rd quote from Virgin (that wasn't price-competitive), but don't have one for Delta.