I love my IWOM. Lots of arguments against it, maybe a few are even valid, but when it comes to being out of the elements while being in the elements, nothing I have tried even comes close.
Biggest complaints:
1. Noise. Non-issue for me with the newest fabric. Its a standard brushed finish. No issues down to single digits, which is the coldest I've had it.
2. Bulk. This one never made sense to me. Look at a guy with enough layers to stay warm in cold conditions, and I doubt you will pick IWOM as the bulky option.
3. Foot containment. I get this one. Not my choice for tiny platforms, and saddle hunting requires dedication and modification. Regular climbing stands are no problem, and its the best thing since sliced bread on the ground.
No leak points, handwarmers heat up your whole envelope, and the price is way less than any equivalent layering system. Packs up smaller than my parka and bibs, and I don't need boot blankets, gloves, or any other accessories. Works in warmer temps as well. Sat this Tuesday at 40°F with rain, wind, and sleet in street clothes and tennis shoes.
Articl Shield is not even close in form or function.
Heater Body Suit is just as warm or warmer, but I prefer a leg envelope and free arms over an upper body envelope and free legs. Personal preference there. HBS might be a touch quieter as well, but is not even close to as weatherproof as the IWOM.
Anyway, not what you asked about, but maybe an option to sort of consider. It took me six years to finally buy one, and now I just wish I had started with it instead of going up the cost ladder with layering systems.