It’s research so it’s good to know how to do it really well so in 10 years you can throw it in. Chasing photo realism is sisyphisian.
Using this now for anything like a commercial game is way past the point of diminishing returns. In their paper the SNR between their solution and default Unity’s blur shader is a couple percent while the computational costs are extremely steep.
At 512x512 resolution their fast solution adds 3ms to render time of each frame using, if I’m reading it right, 4 GPUs, which is a drop in 10fps. That’s mind boggling slow for real-time graphics, especially VR which is even more resolution and frame rate sensitive.
If instead of using the default Unity dof blur you really focused on tuning a blur algorithm, which no one really bothers with because it’s not worth the effort, you could probably make up much of the difference.
But really once you have eye tracking, status quo dof blurring will be more than good enough.
The case they mention where someone would be in VR all day makes sense, but let’s all hope we never reach that dystopic vision.