No concave key wells kills it (and the Fulcrum) for me. The only folks who really know how to nail ergo are Kinesis and maybe MoErgo (though I still haven't seen it shipped).
I've had one for many years. It's my least favourite keyboard. As they rent them out, I would suggest trying one before buying, if possible.
Part of my dislike might come from the MX Black switches they used at the time, and I gather that alternatives are available now. Another factor is their keycap profile and the placement of the switches, which mean that if your fingers get misaligned, you hit a gap between the keys. This is more irritating than it sounds.
While not a criticism at the time it was built, it's also worth noting that there was (and is, I think) no layout customisation other than a choice between fixed layouts with a couple of switches on the underside of the keyboard. The case is vacuum-formed, which looks and feels cheap compared with modern competitors, and the bottom is glued on which would make repairs difficult (not that mine ceased to work).
The staggering is way too small for my hands. The hand will still have to move a lot, making touch typing harder.
I'd also say that the simpler learning curve here is a "faster horse". To reap the significant benefits, one should embrace a different paradigm of typing, with layers and chords.
I’m super happy to see more products popping up in this category. However that looks terrible to type on though. Flat, low and barely any stagger. Also it kind of looks like a toaster. Idk. Not for me I guess, hehe. But still, a good sign!
1. https://naya.tech/