While i seem to be able to pair the two without too much difficulty, have managed to sync contacts, set home number and dial contacts via the nüvi interface, the handsfree function does not seem to work. In other words, for example, if i make a call through my iphone using the nüvi interface, the call gets made but i then have to hold the phone to my ear to the phone as normal (using the iPhone speaker & mic) as the audio does not get routed to the nüvi as expected. Also, while the nüvi is in my list of bluetooth devices on my iPhone 3G, it is without a name.
My experience would appear to be exactly the same as yours Ned. After ages looking around for other discussions about this problem, with no success, i am happy to finally find i am not alone (if regretful of the circumstances which unite us).
Any help resolving this matter would be hugely appreciated as one of the major selling points of the nüvi 775T for me was the bluetooth pairing. I'm beginning to have the feeling it might be a matter of waiting for another iPhone update and hoping that addresses this specific problem though.