I understand your thinking ogs70. My best PE experience was QF63 (day flight to JNB) as I was awake to enjoy the service, room, food/drink...etc. Flying back (QF64) and QF21 last month (both night flights) I felt were wasted as I just tossed and turned and had pseudo-sleep the whole flight so I didn't really notice much of the benefits over Y.
I find I can't really sleep in Y or PE so in the future I'll probably fly Y and just save the money (for a better hotel or a J seat in the future). I too quite like those window-pairs back towards the end of a 777 or 747 (or all of the A330s and A340s) and tend to search for them why flying Y.
EDIT: FYI I've posted two trip reports of QF PE (QF63 and QF21) which you may find interesting. Unfortunately both were old 747s. I'm flying QF128 on Tuesday (which is a refurbished 747 day) in PE (but hopefully upgrading to J) and I'll be sure to post up a trip report in the days following.
http://www.australianfrequentflyer....hotos/visit-south-africa-qf63-qf64-64075.html
http://www.australianfrequentflyer....nd-trip-photos/qf21-syd-nrt-vh-oja-64554.html