The IR works pretty well and fast, no problems with the example scenes I tested.
But I noticed some problems with the volumes.
Simple scene: 3 spheres (ground, one cloud layer, and atmosphere vol. with multiple bounces)
Only one direct light (cor sun at 0° with color temp, no sky), the nightside texture is not emitting light and in a crn layer shader with a lumas shader as the mask.
uhd and pt gave the same result
Left- normal render, right- IR: