I've moved to this method for the past six batches and found a significant improvement in terms of chilling rate and water usage (even though I pump grey water between two drums with a second pump and effectively use nil tap water).
And, yes, I can vouch for the effectiveness of recirulating chilled water (I used 3x2L icecream containers of ice + a few litres of water in an old fermenter) to maintain the chilling rate during the latter part of chilling process ie. when the wort temp drops around the 30C mark. It has to work, because in principle we're chilling 30C wort with 0C water instead of, say, 15C water.
One issue I am yet to properly sort out, however, is wort bubbling in the kettle-out / pump-in hose before flame out. IIRC, JZ suggests recirculating wort for a few minutes to sanitise his pump. My attempts haven't been that successful before flame out, yet the problem has consistently disappeared a minute or so after flame out. A hop change from pellets to plugs/flowers made no difference. Ditto for a change from a false bottom kettle manifold to a pickup tube. Perhaps the wort bubbling is just a quirk with my system (there's only a 250mm drop between kettle-out and pump-in points). I've been scratching my head over this 'bug' for some time. So far, I can only guess that with the wort only a hair's breath away from boiling point, a drop in pressure courtesy of the pump intake (suction), any gases are more likely to come out of solution. Which said, leads to another question I'm yet to answer: are the bubbles air, oxygen, water vapour or whatever?
Of course, recirculating wort before flame out is not absolutely necessary. There are other ways of sanitising a pump - like recirculating after flame out for a few minutes whilst the wort temperature is above 80C. And as mentioned, my problem may simply be isolated to my own system. Or then again, perhaps not? (I'll wait with interest to see what others have found?).
Bottom line, really sold on how effective this system chills, especially down to lager pitching temps. And with the immersion chiller, this system is insensitive to hop or break material leaving the kettle.
Cheers