no. I think it's very useful for 3d programs where you tend to work in the GPU hardware mode, and then occasionally you need to get a look at the final output. But i don't think AE works that way. I don't often have frames that take 2 minutes to render, and even if you do, the render time is probably spread across lots of different things like 3d, lights, DOF, motion blur, effects, etc. I suppose I should use the Draft button more often, but when it comes to switching between speed and quality of output, I usually just switch between FULL and HALF or QUARTER resolutions. That's what i use for the 'region of interest.' I suspect people who work in very large formats for film might find it more useful.