The closest I ever came to doing something with truenames was after a TPK, where the PCs had all been slain in the presence of an artifact that sent all of the souls of those who had died within a 200-mile radius directly to the Abyss (despite wherever their alignments would have normally sent them upon death). Thus, they "woke up" (with no memories of their prior lives) at the feet of Orcus, who informed them they had been his trusted lieutenants but had attempted to oust him from his throne, so he slew them and had them raised in the bodies of mere mortals as penance. They now had to work to regain his good graces, so he sent them out into the various planes on assignments to further his goals. After a couple gaming sessions of that, they encountered the father of one of the PCs (he'd been slain years before and had become a celestial in the meantime) who recognized his daughter. When calling her by her real name - her truename, for Orcus had assigned the slain PCs names of his own choosing and they hadn't known any better - all of the memories of her previous life came flooding back. This allowed her to call her companions by their own truenames, which restored their own memories, and then they spent several gaming sessions undoing all of the evil things that had just done thinking they were demons in Orcus's employ.
Johnathan