Compositor nodes appear in Sequencer pane and allow you to slide input/output nodes in time. As a side effect, IPOs for other nodes could be available for time and other adjustments.

Similar to Shake's Time tab.

The ability to chose Scene Strip render quality, i.e.: wireframe, shaded, Game Engine (using GLSL) would make for a killer Previz and Machinima app.

Previz for animation relies on rapid turnaround of iterations. Being able to choose the render type would speed up renderings dramatically.