Nitrous is still a good viewport render, but one big annoying aspect of it compared to many other modern competitors is that the viewport cannot produce instant image-based lighting (IBL) without progressively iterate the end result over time. While the end result looks good it is straining having to watch five seconds of flickering as soon as you nudge the viewport navigation.

Many modern real-time engines like Unreal can lit and shade scenes from background images in real-time without the need for progressive refinement, so we know it's possible. To increase Progressive Fade Time lessens the flickering a bit, but then you have to sit even longer to wait for the final result. It's a bit frustrating.
It's time to update this archaic aspect of Nitrous. It would definitely make 3ds max feel more mature and up-to-date.