I have had a bluetooth head unit for the past couple of years in my XJ, I bought one of the first Jensen head units. It paired up with my Verizon E815 in 5 seconds, my RAZR in 10 and works well, provided the windows are rolled up
The Jensen has the microphone built into the face plate and on the jeeps, TJ's XJ's and ZJ's the radio is up high so it works out ok for the most part, Sony head units also have the mic built in there. Only the Pioneer and JVC offer a seperate mic that you can mount anywhere which is a better setup. Even with the windows down you can still hear very well, the phone volume is set separately from the tunes volume. Downloading your phone book is dependent on how much your provider has castrated the phones built in features, Verizon castrated their bluetooth feathers quite a bit, they do it to prevent you from being able to do your own ringtones and such so you have to buy from them. I've looked at other providers and kind of a rule of thumb, if they sell ringtones they castrated blutooth for their own gain.
Here is the JVC, has usb too that you can mount where you want, they are cheaper than jvc shows
Or go to www.crutchfield.com
, car audio and pick bluetooth, 22 or so choices there. I would not buy a head unit without it now and I don't like those add on BT units. The Blaupunkt Hamburg MP57 looks like a good deal, got USB and a separate microphone too. I've never heard anthing negative about them except they seem to get stolen alot.