I won't say the host reboot issue is gone. But I will say its not pervasive and from reading, I'd say its no longer a common problem. The issue was that the graphics cards weren't responding to device resets like they were expected to.
I just got this setup. The biggest issue I had was I wanted to use Ubuntu (linux mint actually) and almost every guide is written for arch or fedora. I'm sufficiently new to linux I couldn't easily adapt the guides. Another issue is most of the guides are actually old and do things in a complicated way that doesn't seem necessary anymore, if it ever was.
Brief overview. The hardest part is selecting the correct hardware. After you need to set some modules to load on startup. (kvm, vfio or pci-stub), set a kernel parameter to turn on IOMMU and get devices for passthrough bound to the pci-stub or vfio-pci driver. This is the cumbersome part IMO and could really be improved. I think the main problem is vfio-pci and pci-stub aren't part of the kernel (they are separate modules) and don't always load early enough to grab the hardware before other drivers do. Fedora seems to have a parameter to force it to load early, but there doesn't seem to be a working one in ubuntu/debian?.
Once you win that fight though, most guides seem to suggest building scripts to create VMs which is pretty cumbersome. I think that is obsolete. All I did is install virt-manager, create a VM, install windows, shut it down and add the devices I wanted to the VM. I leave a virtual video card behind, the passed through is a secondary card...which works fine after windows starts. I booted up and installed their drivers. And then I was done. I use a KVM to quickly swap to the VM but there are other solutions.
I will say I found ESXi easier to get up and running (and ESXi 6 actually has some nice improvements here) but its really not designed to be a good tool for this particular kind of setup.