I've been playing long enough to have used the round Wall City bags. I've got back problems and I'm better thanks to surgery but I still deal with some pain. I've got a little boy so I can't use a cart but will some times hang a small bag off the back of his stroller.
I have a Revo Carolina with Phoenix quads. Very painful (for me) to carry it but it makes a great cart bag.
I've borrowed my wife's Grip bag for a few round and I think it is fantastic.
The latest run of Flaks look like a huge step up from the first runs. I haven't worn one or used one for a round but I'm considering one to replace my Revo. If the Flak is on par with the Grip as far as comfort and support the Flak will be my choice because I think I can put my Cannon 60D in the top compartment.
I also heard a rumor of someone else entering the bag race. Problem it, I would like a bag soon and it seems like nothing good comes from having the first run of a Bag, Both Grip and HyzerBomb have made improvements from the first run to what they have now.