Here's a little test I did using a hi-res model of a Honda Pilot. The model is over 600,000 polygons. Not the best model to use for a wide shot like this, but with Multi-Instance it's not a problem. This is a simple grid of 1,000 cars with a little randomness. That's over 600 million polys! Not to mention it's fully textured including chrome, glass, rubber, etc. Setup using Corona and only took 3 min. to render. All lighting is from the HDR you see in the background.
Very impressive.