It would appear that many people have had issues with the update - EGR failures amongst others - engine rattling, low power, MPG through the roof, vibration etc etc and VW seem to be brushing them aside and saying that the failures were probably about to happen anyway!
IF anyone's interested there's now a FaceBook Group (The Volkswagen diesel customer forum (Emissions scandal))
https://www.facebook.com/groups/955027937948541/ who appear to be dedicated to make VW/The Press/The DOT sit up and listen and - of course - the more the merrier.
And remember- ITS NOT ILLEGAL TO NOT HAVE IT DONE - .......yet!
Some people have specifically stated to VW that at service time they DO NOT want them to update the software (it's supposedly irreversible), but it has been done against their wishes and are now driving around seemingly in a bag of nails - All enjoyment has gone and performance down.
I would suggest if you get the 'invite', not go ahead with it until the fiasco is sorted and please join the above FB group, the more people complaining with one voice the stronger the impact.