On my 2.0CR DSG I can't tell at all unless I switch off during a regen.

No increased rpm, no rough running, no noticeable loss of power.

Cheers

Lee

The bigger engines give almost no indication of when the regen is taking place as you say Lee. It's more noticeable on smaller engined cars due to the extra load it places on the engine. But again it depends when it happens as to whether you notice it.