How much trouble is getting Nvidia to work on a BSD? I'm considering switching but I have a similarly high-end set up and it would be a shame to let that hardware go to waste.
The nvidia drivers are a binary blob surrounded by a FreeBSD src-based shim layer. If you're running a -release branch, you just install the nvida driver pkg and you're done. If you run -current like I do (with no KBI guarantees) you re-build the nvidia port every time you update your OS.
All in all, the nvidia drivers "just work" and are very boring. I'll pay a premium for boring.
The NVIDIA drivers work fine for graphics applications.
Nevertheless NVIDIA CUDA is available only for Linux, so NVIDIA GPU compute applications do not work directly, but maybe only using the Linux compatibility layer (I have not tried that).