When you first turn on a GPS unit, it acquires all the satellites that are in range. This can take up to 10 minutes with any GPS unit. Once the sat info has been acquired, getting a fix doesn't take long at all.

This is exactly the same behavior that I found with the N810. Turn on the map software, leave it in the window sill or on the dashboard for 10 minutes. The next time you turn on the mapping software, acquisition time should be short.

I'm here in the middle of a modern metal framed office park building (truly in the middle. I see no windows from my cube) and my N810 is giving me a location in less than 22 seconds. That's starting the timer when I click the Map button on the menu and stopping it when the map changes to my location. If you're having trouble with the GPS, you might have a defective model, but there's nothing wrong with my N810. The sensitivity is higher than with my Nokia LD-1W that I used with my N800. I was never able to get a lock in this building at all with that device.