I've always been a fan of Google for their search engine but in this case, on a Windows Smartphone, getting directions, traffic information and location information is much better with Windows Live Search for Mobile than Google Maps. It makes sense because the same company that wrote the OS for the Smartphone is also providing the service and client.
Unfortunately Google Maps is pretty clunky under the IBM JAVA client, and if you go to here with your Smartphone, you can download the Windows Live Search native client, which can directly interface with a GPS unit and other nice features.
Gizmondo has a much better writeup located here which tipped me off to the Windows Mobile native client.
Now I just have to save up for a Sirf-3 Bluetooth GPS unit.