For me, the important features in a backpack are:
1. Convenience. Quick and easy access to all of my stuff with minimal hassle, and minimal zippers, 2 max.
2. Light weight, the right size, not too big for convenience of toting around in the car and not to small to carry everything I need.
3. Quality, to last long. Good zippers that zip open and closed easy and reliably. Some backpacks use cheap small gauge zippers, which can break easy.
4. Comfort. Good padded shoulders straps and a good waist belt are key for those long hikes, or bike rides.
5. Configurability, the versatility to change the interior configuration around as your equipment evolves (antenna mod, boosters, tracker, wind meter, SD holder, etc).
6. Good value, price right, considering the quality.
7. Adequate protection for the craft and radio. Notice I didn't say maximum protection, because that requires molded insert, which comprises versatility.
8. Airline compliance, 22X14X9", smaller or close to these numbers so you won't get rejected at the gate. Checking isn't an option in my book, the backpack must be compliant.
9. Two handles, one on the top and one on the side. You'd be surprised how often both come in handy.
10. Soft pack so it doesn't beat up my car, no hard shells.
Think Tank Helipak ($149) comes the closest to my ideal backpack. That's what I would buy again. ProCraft ($129) comes in second, but it's slightly too big and the main zipper isn't as rugged, but I own one of those too. Other drone backpacks I've bought and return include Manfrotto, Lowepro, Microraptor, and PolarPro (Trekker version 1).
I also bought the Chinese Cheapy and used it 9 months. It was OK, very lightweight, but the materials were cheap and it wouldn't hold all the stuff I needed to carry.
