Peters reply is absolutly spot on and sums up my stance perfectly. To brag about efforts to fool the (out of date) smoke test is laughable if it was not so serious.
Yes, there are problems with DPFs, I have had Qashqai in here with DPF problems as dsescribed which required forced regen and dealer software changes. Nissan did not help their cause by advertising the Qashqai as the 'Ultimate urban vehicle' or something similar!.
We very regularly do on road regen on BMW and in just about every case it is the driving style/pattern which has contributed to the problem, We had a driving school BMW which the dealer had changed the DPF already and he had further problems with it, Forced regen ,software update and use the correct oil changed more regularly and he has had no further problems in over two years.
I have access to an industrial oven for those DPFs that will not clear with regen, they are 'cooked' at 600 deg C + and the ash then removed, just like the HGV market. In all cases though I sleep well at night because I have not chosen the cowboy route of some which is soon (thankfully) to be made illegal.
I do remember when the MOT test emission values were tightened many years back---Metro could not pass the test without removing vacuum advance and bringing revs up---As advised to do by the VI at the time,!!. Hopefully a similar ridiculous situation will not occur this time round.
We have not even started to discuss the importance of the correct low ash oil as required for all DPFs, manufacturers excessive service intervals, supermarket fuels etc etc.
Peter, you will have to move it all to the left again soon!