Well, you have to download the maps (there's a single site you can download it in chunks with). For what I've used it for, I haven't had a problem with it yet. I haven't had to travel out of Florida yet, so I just downloaded the Florida map.

The maps themselves are part of some open world mapping project, and as far as I know, they get updated pretty often/regularly. However, you kinda have to do the actual downloading yourself, it won't check for you, as far as I know.

That said, because it's a community thing, it also means that if you have the motivation, if no one else in your area has ever contributed map updates, you could do so yourself. (The N900 actually has a tool that is meant to help people who make maps for said project map their GPS coordinates in a way from which map data can be made... but that's a bit on the technical end, and I myself don't know how to do it, just know of it and understand the idea in layman's terms.)