I mainly work in animation, so when setting up scenes i spend a bit of time trying to optimise the render so that I don't turn up to work next day and find "rendering frame 2 of 750, last frame 9 Hrs 47mins" for my overnite renders.

What would be really helpful is a way of seeing how long was spent doing what: updating geometry, moving object, raytrace optimisation, rendering transparent or reflective objects, rendering hypervoxels etc. You see this info on the LWSN nodes, if it was possible to keep it and analyse it after the render it would mean I wouldn't have to guess how many ray recursions I can get away with. Stats on memory usage (like you get in After Effects) would be nice too.