Back in April '08 I wrote that I thought the ability for a GPS to pair with a Bluetooth phone was not one of the most useful GPS features available. In the interests of full disclosure, I deemed the feature “dumb”. In August, '08, I bought my wife a Garmin c550, which has this ability. For someone who doesn't like the Bluetooth headset concept, a Bluetooth speakerphone is the better option than holding one's phone up to one's ear. The c550 displays the caller-ID, on the GPS' screen, making it simple to easily see who is calling, without having to scramble for the phone. It also makes the phone's (an LG Dare, in this case) contact list, recent calls, and other information available via the GPS unit's screen.
As of this writing I have paired it with her phone, and tested it indoors, but we have not yet road-tested the feature.
I still stand by the idea that playing music, through a portable GPS' speakers, is useless to me, but I stand corrected about Bluetooth phone use. Time will tell whether the caller/callee, on the other end of the connection, will actually be able to hear us, but I may be willing to sacrifice that, for quick calls, in the interest of driving safety.
For a full listing of the Garmin c550's feature set, see the TigerDirect link where I bought her unit, at http://www.tigerdirect.com/applications/SearchTools/item-details.asp?Sku=G145-0068 .