There is an NVIDIA web driver update now for the Mac Pro 3,1 and LiteIcon now works as well, which are the two bits I was waiting on. Every version I’ve used of 10.13 seems stable on my MacBook Pro 9,2. So that means it’s probably time go ahead and update the Mac Pro 3,1 to High Sierra.
UPDATE: The NVIDIA web driver doesn’t work. There’s no CUDA for it, and that seems to matter. Going to the OS X native driver has serious issues with things as simple as window drawing. It seems to play video okay, but this is probably utterly useless to me, and I’ll probably need to go back to the Sierra unless a new web driver and CUDA driver combination show up.
UPDATE II: Tried several different things. No joy. Even though the standard macOS drivers should cover my GTX 660, they don’t. I get all sorts of weird icon oddities and window drawing sometimes totally freaks out. There also occasional video delays. The Mac Pro is my video editing machine, and I can’t really have these kind of errors while I’m editing, so I’m shunting the High Sierra install over to a separate partition and restoring this morning’s clone of Sierra. The new bells and whistles just aren’t THAT important for this machine, because honestly, the differences between Sierra and High Sierra are so small in end user experience. If this issue is resolved in a future update, I’ll try again.