I just recently ordered the 5.11 MOAB 6 and I've had it on a few hikes. It's an ideal size for a day pack, and is very comfortable. I wear it on my left side, and it stays snug against my back just above my belt line. There is very little movement of the pack as I’m walking or turning on the trail.
I was using a Maxpedition Sitka Gearslinger before (which I like very much), but it was more pack than I needed for just a day in the woods.
In the photos that I've attached you can see I added the Tier System connections that came with it, plus a couple of paracord loops with roundcord locks. I drape my rain jacket over the top and sides of the pack, then tie it down with the straps and paracord.
A 32 oz Nalgene bottle fits nicely inside, with room for my EDC organizer and first aid kit. There’s even room for a small lunch container.
To keep the weight down, I include just the following items for day hiking:
Compass
Folding knife
Fixed Blade knife
First Aid Kit (plus ACE bandage, latex gloves, finger splints, ice pack, heat pack)
Flashlight
Hand sanitizer
Water bottle
Stainless steel cup
Fire Kit (Matches, tinder, BIC lighter, flint & steel)
Multitool
Pen
Sharpie
Notepad
Power bars (2)
Water pure kit (coffee filters, iodine tablets)
Paracord (25 feet)
Repair kit (Duct tape, rubber bands, tie wraps)
Carabiner
Micro light
Signal Mirror
Space blanket
Neosporin
Light stick
Flashlight batteries
I’m very pleased with the pack and would recommend it for 1-day hikes or an everyday carry.