After all of the questions about MoBridge versus Fiscon bluetooth units, I contacted Volkswagen UK about this.
The answer i got was that VW is well aware that the current OEM Bluetooth unit, which only allows rSAP phones to be used, is inadequate. They've been inundated with complaints. Guess what, they're working on a new unit to be installed within the RNS510. We should see something later this year, I interpret that as for model year 2011.
If this is an issue that bothers you, do take the time to contact VW and complain about the current OEM Bluetooth unit. The more pressure they feel, the faster they will respond. I'll go as far as to say that this should be an issue that bothers all of us. Very few of the people lashing out £30K on a new GTI with an RNS510 are satisfied with a simple old Nokia phone. We're a bunch of fully paid-up card-carrying members of the Blackberry / iPhone / smartphone club. More than that, the Police are coming down much harder on people who use their phones while driving. So we need a reliable solution for handsfree calling. If your phone doesn't properly integrate into the car and you have an accident while fiddling around with it, guess whose fault it will be? Not VW's.
So, IMHO, a new Bluetooth unit cannot come quickly enough. What to do in the meantime? Don't order the OEM system if you have a non-rSAP phone. Get either Fiscon or Mobridge or Parrot. (Apparently, the Parrot system is also very good and fully integrates with RNS510). Dealers will be able to retrofit the new system quite easily when it's available. Hope that helps.