I can't speak to the hardware; I tried to buy a big beefy workstation from them, too, but they don't ship big stuff to Japan, so I commissioned a modern workstation build from a local PC builder instead.
Pop OS installed as easily as everybody says, supporting the NVIDIA RTX 3060 video card, Intel Core i9-11900K (of course), and a recent-model PCIe 4.0 SSD that reads 7GB/sec.
I couldn't figure out how to make it drive a 6K display over Thunderbolt, though — it might be possible, but I "solved" the problem by getting an older Dell 8K display (the real old one that needs two DisplayPort cables). That works great.
TL;DR is that I love it, Pop OS is nearly as polished as macOS or Windows is these days, and it is way faster than any Mac for daily programming, building node apps, reading this site and stack overflow. (I'm coming from an iMac Pro and and M1 Mac Mini, and it is much much much faster than both of those. I think the M1 would feel more competitive if I could use ARM-native Node 16, but most of my work involves Node 14 which runs (slowly) under Rosetta on the M1.)
That would all be true if I just installed Ubuntu, too, though, and presumably Manjaro or (with more reading and fiddling) Arch.
So why do I like System76 and why did I choose their OS? One, I want to have some company trying to make an OS for people like me, and I want them doing that to make money in a non-gross way. So not like giving me a free Google OS to serve ads to my kids.
I feel like System76 is targeting me as a customer. I am willing to pay a premium for a good machine that somebody designed. Not all of their hardware appeals to me, but they are trying to do that.
Likewise, even though the Pop OS improvements on top of Ubuntu are just a handful, I am happy not to have to pay with my time to set those up. For example, fast disk encryption is absolutely fundamental, I enable that on all my machines from day 1. Yes, I absolutely could google it and do it on other flavors of Linux, but still I appreciate that Pop OS makes it a checkbox during the install (like Mac).
Ditto for the Pop Shop (their app store). It's actually not very good — there is hardly any info about the software and updates. So I am not that happy with that aspect, but still I am happy that they are trying to do that.
So I feel like System76 is trying to serve customers like me. I don't really want to allocate my time to tweaking Linux and comparing tiling window managers.
I want somebody with good taste to give me a well-thought-out set of defaults. And preferably that should be a company with a commercial incentive that is also aligned with my personal interests.
I don't think I am like, way happier than I would have been just installing Ubuntu — it's about the same. I'd still be happy. But Ubuntu doesn't seem like they are aiming to please users like me. I am just one of many user demographics they target, and I am also not their customer. I don't pay them, and if I did it would be a donation and be weird.
So Ubuntu, while I appreciate its existence, doesn't give me that little tingle of "wow, cool, these guys are trying to make products for me."
Which is why I ordered their ludicrous made-in-Colorado keyboard. Ultra-configurable keyboard made from heavy slab of metal, with full RGB lighting and multiple USB 3.2 Gen 2 ports in both Type A and C flavors? Yes!! Sign me the fuck up! That is precisely the kind of keyboard I want.
So basically, I think System76 is appealing to users who want to use Linux, but want it to kind of 'just kinda work' like a Mac. They seem to be a scrappy little company you can root for, too, not a huge (and therefore, inevitably, increasingly evil) megacorp like Apple.
So I "like" System76 because the image they've projected via their website, reddit, etc appeals to me. I want them to keep trying to make products that I want, and I want to buy those products, and I want enough other people to also buy them that System76 succeeds and this commercial relationship can continue to our mutual benefit.