Their GTX series cards all used proprietary blobs that required unmanageable device specific interfaces.
Starting from the RTX series cards, they still have proprietary blobs but instead of having device specific interfaces, they all use a shared public interface which makes compatibility and performance much better.
It's not across the board, but there are instances of gaming benchmarks showing more performance under linux than windows.
Now, it's been barely a couple of months since I reinstalled Ubuntu, and a couple of weeks since I found out the latest release runs even worse, so this is new to me. I don't plan to use Windows at home ever again, so I could sell my GPU and buy AMD, but so far I'm simply disappointed.
I'm convinced that many these people saying Nvidia has serious issues on Linux must be (by no fault of their own) going by habit and downloading the driver installer .bin from the Nvidia website and trying to install drivers that way. So yes, if you do that you're going to have issues.
Learn to do things the way your distro does them (use a package manager) and most problems go away.
It's MOSTLY painless. Some GNOME extensions seem to randomly hang everything on startup (I'm currently investigating which ones, I believe Dash to Dock and/or Unite are to blame) and there's a weird issue with VR when streaming via ALVR: SteamVR launches, but games crash unless I disable the second monitor (no such issues with WiVRn, so not entirely sure if it's a driver problem or not)
Besides that in my daily driving I saw no other issues.