I may be able to address a couple of those points 6speed.
Third tank just topped up by about 60% for a busy weekend. Based on diesel used, mpg was better than the first couple of tanks but not back to my usual 50. Engine does seem quieter and the early morning (6am) cold start rattle is no longer there (wasn't that significant before, just not there at all now). I have used the last of the 2T in topping the tank so after this I am running for 3 tanks with no additive.
The DPF burn frequency does not seem to have been altered significantly although on the Accord, it is hard to say when it has kicked in. I keep an eye on the on-board computer to see when the instant mpg drops significantly, then comes back. It may - may - have reduced the frequency by 10% but that is too small a margin to be a reliable stat.
Power around 1750 - 2200 rpm is definitely up. 2nd gear wheel spin is something I haven't tried for but has happened a few times now.
So, my conclusion so far is that after 1700 miles with a variety of driving styles, mpg is down, quietness is improved, power is up. Is it worth the £3 (approx) per tankful for the 2T and the reduced mpg (circa 4%)? Inconclusive.
I'll report back again when this tankful is gone and replaced with straight Tesco diesel.
Edited by - velocityblade on 25 Oct 2012 14:45:54