I've bought a couple of System76 laptops used on eBay and they did have some hardware issues but they were still under warranty and while I had to ship the laptops out they were both fixed promptly and continue to work to this day. Its also nice to have Linux be supported by their support and who help you avoid all of the hair pulling insanity that can come with getting various drivers to work on any operating system. My Oryx Pro is one from two generations ago and yeah it is closer to a portable desktop than a mobile laptop but it is nice having all of that power in one box. I mean Linux power management on a core level hasn't received the love that say optimizing Linux server workloads has, so battery life is always going to be somewhat lacking especially with a massive GPU, so you have to keep it plugged in.
