One thing I have always appreciated in various navigation systems, is the fact that they show you the maximum speed for the road you're on. I'm one of those guys who doesn't read signs too much (there's too much of them here in the Netherlands, so you learn to ignore them), but this also results in me guessing the maximum allowed speed.
It could just be something that users can enter when updating the map on their computer, just like the name of the street.

I would very much appreciate the addition and I would be willing to add the information to most of the streets in my home town (at least the ones for which I know it).

Regards,
Michael