The XDA-Developers WIKI has a new addition which provides detailed instructions on how to enable AGPS on your HTC Titan/ Verizon xv6800. AGPS is an add-on to normal GPS which provides for faster or even instant GPS locks using data provided by Verizon’s own servers. While normal GPS can take from one to two minutes to get a lock, with AGPS instant locks even indoors is possible.
The procedure appears pretty complicated, so a read of the associated thread is recommended, but users who have implemented have certainly found it rewarding, as it makes the use of applications such as Google Maps and Windows Live Search much easier (vs launching the application and waiting 1 minute before you get any results).
Read the WIKI article here for further information.