Yup .... in Canada (and I believe the US), the deflector is 1/2 the price if you buy it as original equipment when you purchase the car, as opposed to after the fact; so if you want one, get it when you buy the car. They do work, cut down noise, and foot drafts, as well as provide a method for visually securing stuff in the back seat. The unit folds up and stores in the trunk when not needed ... but they are expensive!!!! Was unable to find an economic after-market, so was forced to get from VW! Frankly, I think it was a bit of a rip-off, but there appears to be no alternative so far.
Definitely a good buy. I was driving in the mountains today, between 5-7c, and tried both with and without the deflector fitted. No comparison, when it's there it stops the wind going into the back of the car, and then between and under the seats to get to you, never mind the back of your head. Expensive, yes, but it works.
I'm sure the regualr folks remember my mission of the rear deflector when I got my car. Not sure where you are located, but depending on where you are you may be able to get one (even after you receive your car). I had success getting mine after I got my car when I Called VWoA. It is about $570 US and I know I would be deterred from getting one if I had to spend that much. But Gurny is right, no comparison. My wife and I can have a normal volume conversation at 70mph (120kph) on the freeway with both deflectors and the windows up, not to mention it is also nice when there is a chill in the air. Try to get one from the dealer as a throw in if your car doesn't come with one, otherwise try calling VW direct. That is what I had to do and it worked great... free of charge.