Excellent is a stretch. It works for things they support. Look at optimus and wayland for instance. Also, they restrict nouveau from working by signing blobs and enforcing checks. And this is years after Linus flipping the bird and other repeated requests.
Optimus was the single most pain in the ass thing I have ever experienced in linux. Never again, am I going to run linux on an optimus machine with Bumblebee.
I don't know, I upgraded to 18.10 and my XPS's brightness control doesn't work. The Prime switchy thing can't change cards without a reboot, and if the screen goes to sleep between switching cards and rebooting, it never comes up again. Actually, with 18.10, it never comes up again anyway. I have a whole host of issues with nVidia cards, my next card is going to be AMD.
That's not the point. The switching issue at least is present on 18.04 as well. Basically, ubuntu changed the mechnanism from bbswitch in 16.04 to a different one in 18.04. The 18.04 one is buggy and inferior at the moment.
Their driver is really behind in terms of supporting newer libdrm features. It's also not well integrated in the ecosystem. They basically don't talk to the other Linux graphics devs.
