I have the Icon Pro 1850 bag. I use it either with the carbon fiber frame and an Ultra suspension (I also have an Ultra 3000 bag that I use with the frame), or I use the shoulder straps and belt from the Ultra suspension with the internal supports on the 1850 when I don't need to haul weight.
My rationale: I used to carry my Assault II attached to the Kuiu carbon fiber frame. I zip-tied the frame and suspension to the stand (in place of Molle straps) because the whole thing weighed like 2 lbs and carries weight way better than Molle straps and belt). Then I would attach the Ultra 3000 bag to the frame, but over the stand, for my other gear, clothes, etc, and I even threw my Wild Edge steps or Muddy Pro sticks in the bag to reduce snags. Worked great - the whole thing weighed less than 30lbs and carried well because the pack is designed to carry a lot more weight than that. When I reached the tree I'd just take the bag off the frame, take the steps/sticks out and then just hang the bag off my saddle as I climbed, then hang it from a hook in the tree at height. The suspension and frame stayed attached to the Lone Wolf (again, like Molle straps), and I just wore it while I climbed and then took it off my shoulders when I got to hunting height and hung the stand.
I ordered an Icon Pro 1850 because I wanted a pack for turkey hunting and saddle hunting when I wasn't going to pack out a deer. I can use the bag on the frame if I want, but usually I just use the internal stays and use it as a day pack (Ultra doesn't have stays or ability to attach suspension without the frame). I can fit an 8 WE step bag with the steps, plus my saddle and all the ropes in the 1850 easily, along with knee pads, knife, head lamp, etc., extra clothes either get stuffed inside or strapped to outside.
That way I have a 10-15lb pack weight and I can hunt all day without noticing I'm even carrying it, but I have the option to climb a tree if I want.
Late season I'll probably go back to the 3000 bag, because I can fit my Sitka Fanatic jacket and bibs in that bag, along with the steps and saddle, which I can't do with the 1850 (those clothes are crazy warm, but they don't compress well at all, and I'm definitely not walking more than a few hundred yards with the Fanatic on...)
Anyway, once you get used to a western style frame and suspension, and using a bag that is separate from the actual pack, it opens up a lot of possibilities. It just takes awhile to get used to all the straps and attachment points. And, when you don't need the meat shelf option for either packing an animal out or for a stand, the 1850's option to be a stand alone pack that still carries weight pretty well is a nice option.