Yes Rawalanche, but also resolution is important. And, much better if, with the same exact resolution, I will be able to draw a region, like in VRay.
So ASPECT RATRIO + RESOLUTION + DRAW REGION = perfect IR
Why? Because, with IR, I will be able to render exactly like in Production render, but with the flexibility of IR itself.
Like IR is now, I can have just a raw (very raw) preview on-the-fly, but without correct aspect ration and resolution.