I have visited this issue several times in the last few years.
I too did a ton of research and have purchased NUMEROUS packs.
I have a small fanny pack and a HUGE pack that carries everything.
I think I have discovered the ideal
I dont know why no one has ever suggested it.A Camelbak
I have the HAWG, http://www.camelbak.com/Sports-Recreation/Packs/2011-Hawg-NV.aspx
it includes a rain cover (many dont and this was a requirement
Many packs I have used/tried have very poor suspension systems.
This pack fits like a pack should and carries 3 liters of water.
If you dont want that much or any water leave the bladder out.
Here is what I pack in it when I want most of my gear (or hopping on the plane)
D40x, 12-24mm f2.8, 50mm 2.8, 18-55, and 50 - 200. and a 1.5x teleconverter
SB-600 with remote (6') cable, white balance card, air blower
filters; polarizer & grad ND for both lens sizes, and a 4x6 handheld polarizer.
Two extra batteries, 4 CF cards and likely more I can not recall right now, but you know the "usual" stuff
The pack does not have the padded "compartments" of a photo pack but I use padded cases and pack it correctly.
When I fly the compartment for the bladder (padded and insulated) carries my computer and a hard drive.
Needless to say the pack will hold more than I have in it.
When hiking I usually have some foodstuff and a foul weather gear attached to the back.
There is also a large expandable area on the back designed for a helmet.
The two side pockets hold smaller stuff.Tripod
I just recently purchased a Benro Travel Angel but have not used it yet.
I liked the idea of having a monopod if I wanted it w/o carrying something else.
That said having a tripod with me I dont know when I'd opt for a mono pod?
Regardless I always travel with my tripod attached to the outside of my pack.
I usually hang it off the pack's carry handle (a looped length of cord works fine)
And then strap the legs together and to the bottom of the pack.
Hope this helps