First off: I've found Waze to be the most accurate and useful nav app on my phone. It's hands-down better than mapquest, google maps, etc. Great job! My only real complaint is in this thread so I'll add another voice, er face, uhm name, eager for this feature. Watching the map spinning around my car drives me nuts and is actually far less intuitive for me than north-up (never mind the implied arrogance of expecting the world to, literally, revolve around you.
Most people may not enable north-up if it's there but most people also use the browser that came with their OS even when a better one is available. And I would bet that the users who want this feature are more likely to be very interested in navigation so they'll also be your most fervent fans.
Thanks for your time and keep up the great work!