I just had my HTC Titan jailbreak'd. First you have to flash 2.05 SPL and then flash HardSPL before you can install any unlocked ROM on your device
it took me less than 30 minutes to complete all steps.
however, for AT&T branded titans, you may need to use goldcard and y-cable instead... so it could be a little tougher to do the jailbreak process for you..the same goes with htc radar which are AT&T brand..
here are some benefits of having an application unlocked device:
-installation of homebrew apps (.Xap installation packages)
-bt file transfer (just install the xap file for this one)
-customizable sms alert tones (again, just install the xap for this)