I use mine lots mainly for work. Had mine about 6 years now and has still going strong and gets a lot of abuse. it currently has in it:
All kept in a waterproof bergen liner
Softie 3
Issue waterproof Jacket (you never know on salisbury plain)
new issue gaiters
1 Rat pack
1 litre water bottle (58 pattern)
metal mug/flask
FA Kit
2 FFD (1st field dressings)
Insulated Jacket
zoot suit (top and bottoms)
spare socks
shemagh
balaclava
gloves
headover
Jetboil
long necked spoon
lighter
spare bootlaces
Survival kit
leatherman wave
gerber recon torch
Madjak Torch (hi power)
sewing kit
boot polish and brushes
hi vis vest
notebook and notebook holder (pens and pencils etc included)
Black Nasty (fixing tape)
insulating tape
comms cord (30m)
claymore bag
para cord (15m)
red, green and blue cylumes (2 of each minimum)
Bowman radio and spare batteries
Range safety kit (red smoke and mini flares)
and still have room for some other stuff
So I would say it holds enough kit for me and still can add other kit to if necessary