Lemur Pro owner here. I personally have super-mixed feelings about the machine.
Pros: Battery life is excellent. Used it for 12 hours while walking around a factory doing an IT system install, never had to charge it. Slim form factor is nice. With an upgrade to an i7, additional RAM, SSD, etc., performance is good for any task not requiring a GPU. It would easily be the best laptop I've ever owned, except for...
Cons: WiFi chipset died within months of purchase and had to be replaced. Battery swelled by year 2 to the point that the mouse was unusable, so battery had to be replaced as well. The machine shipped with Ubuntu 20.04 LTS, which had a Linux kernel bug that caused the machine to freeze when trying to throttle up/down the i7 CPU for power management purposes. I contacted System76 about the problem, and they didn't know anything about it... I ended up having to troubleshoot it myself, at which point I told them the issue, and they sent out an email about the fix to (what I assume was) all Lemur Pro owners. I thought buying a Linux laptop from a company that specializes in making Linux laptops would let me avoid these kinds of nagging issues around things like drivers and power management bugs, but alas it did not. More startlingly, I would have expected a company that specializes in Linux laptops to at least be AWARE of such an issue on their machines, but it seems they had no idea... I feel like I would have been just as well off going with a Thinkpad.
Related final pro: It was frustrating to have to replace multiple parts in this machine (especially so early in its life), but I have to give credit to System76's self-install policy. They sent me the parts and detailed instructions for doing the repairs myself. Saved so much headache.
Overall, I really want to love my System76, but I'd have to think really hard before buying another one.
Another Lemur Pro owner. Short essence: Casing quality is rather poor, if you like "used look" after 6 months, you may actually enjoy it. Wears off very fast. However being able to modify their firmware (I remapped quite some keys) and given that the battery can run up to 2 business days, I'd consider buying this device again. No hardware/software (using their Pop_OS!) issues since using for it 15 months now. Ah, and I like how slim and light weight it is (roughly 1kg).