Dapeeps,
I have been using Mapquest Nav 5.0 since my days with the Mogul . It took Mapquest about 30 some days to release a VGA version for the TP it came out and I have been using it since then. You be looking at some old link that is still alive....here is link for an OTA dowload of the cab
http://mapquestdtc.telmap.com/ota
Here is a link showing TP as supported:
http://wireless.mapquest.com/mapquest-navigator#Sprint (says coming soon on this page but it is available.