I'm no 'tech expert' but the only indication I have seen of my car (1.9 Jtdm) doing a regen is the current fuel consumption plummeting. It did one just last night for example. Happily cruising on the motorway at about 65 (it was a nice evening) average fuel consumption around the 47 mark and then wallop, down to the very low 20s for up to 5 mins, and then as if by magic, it climbs up again to the high 40s, no power loss, juddering or any other noticeable effect.
Interestingly, I also get a bit of hunting/surging in the lower gears, particularly when I ease off the throttle (coming up behind another vehicle for example). It did this when I first bought the car spring last year so I switched to V-Power diesel and had a re-map which seemed to sort it out, and now these past few weeks its started coming back. Something to do with warm weather perhaps?! At the end of the day, its only a very, very slight niggle for an otherwise terrific car.