Recommendations for the most comfortable backpack

Like the title says, I'm looking for a comfy backpack. Something that can hold a 70-200/2.8, 16-35/2.8, and 24-70 mounted on the camera. I've had many camera bags before, mainly Lowepro, but they all feel like blocks on my back; and they don't get any more comfy when loaded. I'm looking for a bag I can haul around for a couple hours without feeling like I'm carrying a box around. Any suggestions? Color, capacity, and brand can all take a backseat this time as long as it's comfortable TIA guys & gals!

The most comfortable one that I have ever had is the kata-103. I just got back from Tetons and Yellowstone where I pretty much carried it all day everyday, with 3L of water in a camelbak bladder. Best money I have spend. You can pick up a used one for $90 or there about.

my most comfortable back pack is the lowepro primus minimus, pity it's not made any more.
It's got a 8 point adjustable harness with a sternum strap, compression straps and an extra wide and super padded waist belt with cinch straps to take all the weight.

It's a real back pack for upcountry treking, not just a bag or box with straps

http://www.youtube.com​/watch?v=8PEpvQj9VC0

Mine is my f stop guru; designed as a bag first, not a camera box.

Crumpler for me...Both my Sinking Barge Deluxe and my Karachi Outpost (M) are incredibly comfortable.

Ya, I don't have one, but I have tried on many crumpler backpacks and they are definitely very comfortable! They hug your bag unlike most backpacks I have tried.

Thanks guys! The Kata's backpacks look good, I just have never tried one on. I like their slings as well, but don't know if a sling will suit me for a full day out. And yes - the Lowepro Primus is an awesome bag. Had a chance to get one a couple years ago but at the time, I went with a messenger style bag. Still kicking myself over that one.

Kata minibee to the way