Yes, you’re right, V-Ray settings set to Progressive/GPU Acceleration, I’ve got a small peak of 20% on the GPU while the CPUs were between 90 and 97%. 1m45.4s for my test scene.
Settings set to Progressive/CPU and about the same GPU/CPU usage. 1m43.8s for my test scene.
It’s only when the “Interactive” switch is turned on that the GPU gets a workout…