Hello there,
I use my Serval on a daily basis, and I can say without question that it's the best computer I've ever had. The only upgrade I've performed since my review is adding an additional 32GB of RAM for a total of 48GB. It's been able to handle every task I've thrown at it, and since the RAM upgrade, I can multitask a huge amount with it as well.
The biggest issue I've had with it is an overheating problem. To be clear, this does not happen under normal usage– it's perfectly stable when I'm CPU rendering a video or GPU rendering an animation. However, if I try to GPU render an animation in Blender and CPU render a video in Kdenlive at the same time, the CPU temperature will often break 100 degrees Celsius, which causes the computer to immediately shut down. This is a little disappointing, as I specifically asked about thermals before I bought the machine and System76 assured me that they performed "extensive testing." That said, it hasn't been a problem since I now know not to render on both chips at the same time.
As far as build quality goes, I would have preferred it be made of metal, as the little ding in the plastic that I pointed out in my review does make the whole thing look a little cheaper than it really should. However, I don't actually touch the laptop all that often, as I'm most often using it with an external keyboard/mouse/display, so the materials don't really bother me. I do transport it every now and then for events, and it feels solid when closed. The display hinges are still very tight (in a good way), for what it's worth. The biggest con in terms of build quality is the screen's backlight bleed, which I showed in my review.
If I was going to get another laptop, I would absolutely go with System76 again. You just can't beat them in terms of performance. If I was going to get a desktop, however, I would build my own rather than purchasing one from System76 at this time. I'm very concerned with the direction that NVIDIA's Linux support is going, and unless their open-source driver situation changes, I wouldn't buy a desktop from System76 until they offer an AMD graphics option. For a laptop, though, AMD isn't an option for performance, so again, I'd totally go System76, especially because they also have desktop CPUs in their higher-end models.
Let me know if you have any further questions!