Had no end of problems with the DPF on my old PD170. I do a lot of urban driving at times which means it's forced to do a 'manual' regeneration phase now and then and, when it did, I got everything from harsh noise to stuttering acceleration. Had a few software updates during the four years I had it which sometimes made it better, sometimes worse. It often gave up altogether and gave me a particulate filter warning on the DIS and I had to go for a blat down the motorway to clear it.
My current CR170 is much better. You know when it's doing a regeneration as it idles at 1000rpm rather than 800 but, aside from that, it's not noticable and I've not had any warnings.
I think the DPF tech was very very new when the PD170 came out and they've sorted it a lot since then.