First off, I love this ruck. It’s way more comfortable and durable than the MOLLE 4K or 2K, and it lets me pack a lot more than my 4K ever could for missions, FTXs, or 3-day events. I won’t knock the 2K too much, though, I do like how the top can expand or collapse depending on your needs, so you can run it for anything from a 3-day mission to a week-long setup and STILL have space to spare for whatever I need, currently max weight I've ran the ruck at is 75ibs, all I've needed for now.
It’s also really easy to figure out and use. Adding sustainment pouches gives you even more space, which is a big plus. And having a dedicated bottom compartment for the MSS is awesome as hell, it saves me from digging through the entire ruck like I had to with the 4K, especially when the zippers were obstructed or broken on the bottom.
That said, there are a couple of issues. The frame tends to hang a bit low at first if the waist belt isn’t adjusted properly, it can sit below the belt on the EMOD frame and rub against my tailbone. I’m planning to adjust and test that more. I’ve also noticed some rubbing and hot spots on my mid-back from the frame, especially the OCP fabric section. If I’m just wearing a shirt, it can get pretty uncomfortable, so I’ve had to wear a thicker layer like a hoodie or jacket to not have that happen, which, I understand, it's a mission ruck.
Overall though, I’m really glad Eberlestock released this ruck, especially since it dropped just a few days before I bought it. I’m definitely happier with it.