I recently started using the GPS functionality in my AT&T Tilt (HTC 8925).  About the same time, I downloaded a new version of the Microsoft Windows Live Search Mobile (or http://m.live.com from your mobile phone).

Very easy to set up:

1. Download Live Search Mobile on your phone from http://wls.live.com
2. Allow the .CAB file to install
3. Launch Live Search from your Smartphone's Start menu
4. Click on "Menu" and "Settings"
5. You'll want to "Enable speech recognition" and for the ATT Tilt select "GPS COM4"
6. Click on "Done"

That's it!  Now you're ready to GPS navigate on your Tilt (or almost any GPS enabled smartphone as I understand it!):

1. Click on Directions, and choose your "New starting location" from your "Current GPS position" entry
2. Name your location (the default GPS Location will do, but it will ask you to overwrite it the next time) and click Done
3. Then choose your "New ending location".  Because you selected "Enable speech recognition" you can click "Speak" and speak the location, or you can type it in, or choose from your Outlook or SIM contacts.
4. Click "Route" and the route will generate.
5. Once the Route is selected, click "Map"
6. Once the Route Map is displayed, click Menu>Center on GPS

It'll give you turn by turn directions, notifying you with a beep when you get close to your next turn, when you're at your next turn, and when you are on the next direction.

I'm at the point now where I never leave home without it!!!