I love my Nokia N95 but the GPS performance has generally been barely acceptable. The latest V12 firmware changes all that with assisted GPS. The time to acquire a fix has gone from 5 minutes+ to less than 20 seconds, and often in under 10 seconds.
Here is a short explanation of how A-GPS works.
What is AGPS? Assisted GPS describes a system where outside sources, such as an assistance server and reference network, help a GPS receiver perform the tasks required to make range measurements and position solutions. The assistance server has the ability to access information from the reference network and also has computing power far beyond that of the GPS receiver. The assistance server communicates with the GPS receiver via a wireless link. With assistance from the network, the receiver can operate more quickly and efficiently than it would unassisted, because a set of tasks that it would normally handle is shared with the assistance server. The resulting AGPS system, consisting of the integrated GPS receiver and network components, boosts performance beyond that of the same receiver in a stand-alone mode.