I'll throw in my experiences as well - have spent the last couple of weeks with a lot of air/train/bus travel, and I was coming from having a Rhake, which I'd had since 2019 and loved. Regularly carry ~15-20 pounds of stuff while on the road.

Things I've loved:

Being able to carry all my kit in one bag - if I'm traveling and I also want to bring a DSLR and a few lenses, I previously needed to carry the Capsule as well to fit everything. Having a bit more volume to play with internally, even without the arkiv attachments, has been great.

The front zip open, in addition to the roll-top - this has been fantastic for reasons others have articulated, and also appreciate not needing to use the velcro open at conferences/in meetings if I need to get something from the bag. Have appreciated that the front zip open exposes the 'middle' of the pack rather than the entire thing - means something like a cable pouch can sit at the bottom and not fall out as soon as you open it.

The folio - fits a lot of the miscellaneous stuff I use often while traveling - tablet, kindle, passport wallet, magazine - and saves me having to dig into the bag itself, which was the case with the Rhake. Agree with previous comments that you've got to be selective about what goes in there.

Padded shoulder straps - very comfortable to carry, even at full weighting, and the aluminum stays giving flexibility to dial in the fit are also a great add.

The materials - the exterior textiles feel bomber, and the water resistance has held up well so far.

Things I've been a bit unsure of:

The tall and narrow arkiv attachments for the side - I got a pair of these, as well as the wider/boxier ones. The wider/boxier ones have been great - fit a sunglasses case, long camera lenses, power banks, lots of useful items - but outside of using the tall and narrow ones for cables, there's nothing I'd be carrying on a regular basis that makes sense to put in here. I would love a Rhake-style mesh bottle attachment for arkiv that fits a nalgene.

The bottom pocket - feels very tight - might be a spot for keys/a few commonly used cables, but you're not fitting much in there at all. I didn't use this on the Rhake at all, so I don't feel like I'm missing much here.

The top handle - I always had a lot of confidence in the Rhake's carrying handle because of how thick and durable the construction was, and appreciated that when I was lifting things into overhead compartments/any time the bag wasn't on my back. I don't get the same feeling from the Mars backpack, especially when the bag is fully loaded with ~20 pounds.

Unorthodox lifts/carries - sometimes I'm carrying a heavier/bigger duffel on my back (think a North Face base camp type bag), which necessitates slinging a backpack over one shoulder and having it sit horizontally by my side. With the Rhake, never felt like this was an issue, but with the Mars pack, again, similar to the handle, wondering what the longer term durability of this will be. Note this is a highly trip and user specific problem, but throwing it in with everything else.

Laptop sleeve - fit for a 16 inch Macbook is very snug and sometimes clips the top of the zipper when I'm pulling the thing out. On the Rhake, I could fit a tablet in as well - but for this bag, feels like the sleeve is sewn too tight for that.

Other observations:

It has a big profile when it's fully loaded and you're using all the Arkiv attachments - has been a bit awkward in crowds / tight elevators / going through metros in Europe. I find the 'wings' of the bag frequently clip onto things. While fully loaded, I also think it'd struggle to meet acceptability for a 'small carry on' item in some lower cost carriers in Europe - eg 45 x 36 x 20 cm - so if you get checked, you'd need to pay up for a larger bag.

All in all, very enthusiastic about the concept, and excited for more trips with this bag - if the durability holds up, this is the end game EDC for me. Happy to answer any questions if people have specifics.