The Bluetooth is very worth while for a RNS-e even if you don't have a MFSW.
But there are several version of the Bluetooth module and the one in the listing version D which has very basic bluetooth support and I would definitely not buy it. I suspect that the seller bought this and then realised it wasn't suitable and is therefore passing it on, clearly stating the part number but omitting all the facts about the early D version. Ideally you need version M (or later) for everything to work correctly. You will also need the wiring loom to connect this to your RNS-e.
Just keep looking. They do come up on eBAY quite often and I bought my version M for £130 (if I remember correctly) I then bought new antena and microphone from Audi anf made up my own loom.
The main reason for getting the genuine unit is its superb integration with the car. With a compatible phone it will copy all your phone entried along with dialed, received and missed calls etc.
I think it is 'better' if you have the MFSW but it is not essential and works very well using the RNS-e to control everything. Much better than the after market bluetooth kits that require extra dial/screens to be mounted and spoil the OEM look of the dash.
Here is the list of part numbers for all the versions.
PHONE INTERFACE BOX
8E0 862 335 <MY 2005.5 A4 (US) - no Bluetooth
8P0 862 335 <MY 2004 A3 - Basic functionality only
8P0 862 335 A MY 2004 A3/A4 - Basic functionality only
8P0 862 335 D MY 2005 A4 >8E-5-533 000 - Basic functionality only
8P0 862 335 E MY 2005 A4 8E-5-533 001>>8E-5-600 000 - Basic functionality only
8P0 862 335 C MY 2006 A4 8E-6-000 001/8E-6-800 001>>
8P0 862 335 B MY 2006 A3/A4 (US)
8P0 862 335 F MY 2006.5 A3/A4 (Europe)
8P0 862 335 G MY 2006.5 A4 (US)
8P0 862 335 M MY 2007 (Europe)
8P0 862 335 J MY 2007 (US)
8P0 862 335 H MY 2007.5 (Europe)
8P0 862 335 L MY 2008 (US)
8P0 862 335 K MY 2008 (Europe, sw 0340)
8P0 862 335 Q MY 2008 (Europe, sw 0350)
8P0 862 335 R MY 2008 (North America)
(from
www.navplus.us)