I'm using Telenav on my PPC.. I like it because the maps are updated quarterly, and it's easier to take with me. My new phone requires a standalone GPS receiver, but that thing is no bigger than 2 packs of playing cards, and has the advantage of using WAAS.
It does the real-time traffic re-routing and alerting, and you can setup your routes from your PC, or call it in and let the voice recognition (which works well) convert that to the address, if you don't want to type it in on the phone.
On earlier phones it wasn't so good, but the version 5 is pretty sweet...
