I think quite a few will dispute that... although I guess you only hear about the good ones...Of all the 170PD's we have seen we have yet to come across 1 that makes in excess of 180bhp stock and with all the latest factory updates they are all coming out with approx 165bhp.These figures are equated from M/G's of fuel,boost and requested torque level taken from the stock ECU calibration figures.
Ive only had 1 regen in 18 months and never had any sensor or DPF issues again I think you only hear about the bad ones, and unfortunately when there is a problem related to the DPF it seems to cause lots of other issues...
I would definitely wait till after the warranty has expired, its not the sort of thing you could hide from even the dumbest dealer!