The GPS in my N900 works without AGPS, so if there is a bug out there it does not affect my device. I got a location widget on my desktop and it shows my location with and without data connection.

The mapping and routing software supplied with the device (Ovi maps) lacks a lot of functionality and the UI is bad. The maps themselves seem to be accurate, at least in the SF Bay Area.

I also hope for a substantial SW improvement, be it a better version of Ovi maps or a third party application.
My take: A dedicated GPS device is currentlly superior. The N900 with the supplied maps is better than nothing.