Here's what I had in/on there:
Wool Socks
Poncho
Mag block/ferro rod, mini Bic, half piece of Fire Stick
Space blanket
LED headlamp
First aid: (bandaids, gauze pad, ACE bandage, Neosporin, IB, acetominophen, aspirin, Benadryl, iodine tabs)
Mirror
Gloves
Long sleeve shirt
550 cord
DEET
Mini Mag Lite
Bandana
Chewy granola bars
and Keys, because they poke me when I carry them in my pocket.

(I forgot to add my zipper-pull compass from my other rig)
There was a little room left in some of the pockets, and the clothing could have been compressed more. I think one of the reviews at CTD mentioned the zippers failing, so I'd be cautious of over-stuffing. There are still plenty of external attachment points to lash on extra pouches or such.
I can see why they ripped off the Proteus.

It's a pretty handy piece of kit, but it still leaves me with having to figure out how to carry my handgun, digicam, and extra dog water.