I think it has some kind of firmware that manages the backlight, so if you switch between really bright and dark windows a lot (like a browser and terminal) then it changes brightness a lot which is annoying, and there's no way to turn it off. Personally the only thing I've had issues with (on Linux) is the soundcard producing low-level noise because of the CPU going into powersaving mode. It's fixable but I can't remember exactly what I had to do to get it to stop.

On the bright side, it does help a lot for the battery life (I get around 8 hours usually).

I also have an older system76 laptop and I would definitely recommend the XPS (13 or 15) over it if you want something lightweight with good battery life.