I use them quite a bit especially with m'way driving as it saves me having my windows open, Im not a huge fan of A/C, much prefer to have natural air in the car, even if its cr4p air..lol!!
Also pretty good when the little one is in the back of the car.
Only car I have experience of that has the electic rear pop outs is the E46 and thats what got me thinking, would have been such a useful option and something that Audi should really have added to the car, considering it has everything else!!
Ah well...