Great article, I have followed pretty much the same path...
I am down in Victoria, so the Otways are my playground.
I agree with everything you have said/take, most of your gear I have had or have and have only really 'replaced' for lighter versions. Eg:
GPS- I went to a bluetooth datalogger, single button for POI recording and logs for 30 odd hours on one charge, uses a generic Nokia battery so I can carry a couple of need be, I download into the software that came with it that integrates into Google Earth. Qstarz BT-1000 I think it is. 66 grams with battery
Down Jacket- I went for a Patagonia synthetic fill, 383 grams, XXL covers me to top of thigh, fantastic for cold night sitting, or even cool day rest/meal stops. Like you, purchased from these forums.
SteriPen- 159g with set of spare nimh batts, carry 500-1000 ml and sterilize on the way. Mind you I am in the Otways where it (usually) rains every day!
Aarn Pack- Natural Balance, an absolute joy to walk with, at 1990 grams it aint light, but the comfort and load carrying ability is unbeatable, it is totally waterproof ( I have towed it behind my kayak all day)
I could go on...
I think the main point is to 'try' everything and work out what you want, the 'got to be the lightest' philosophy is a personal choice, one I do not want to follow, if I am comfortable, well prepared, and enjoying myself, I don't care!
If you have the means, get into MYOG, the satisfaction of sleeping/hiking in a tent, sleeping bag, pack, poncho you have made is second to none!
Keep it up Andrew, and remember, if it works for you, find the lightest possible and go for it!