If navigation/mapping is a bust on the N900, I will be very disappointed. And if I can't use navigation/mapping without a data connection, I'll be upset (and, based on some reports, it looks like I will indeed be upset).
Basically, my expectation/hope for the N900 would be something like this: Ideal N900 = updated N810 + updated Maemo + voice calls + 3g data + GPS & mapping equal to Verizon Droid
It's a bug https://bugs.maemo.org/show_bug.cgi?id=5337 and hopefully it gets fixed.