Well, had it done today and I do think its better at the bottom end, less inclined to stall at start up and pulling away. It seems some how smoother and less vibey. Not sure about the top end though. Interestingly, on the way home the MPG got better by 5mpg on exactly the same route I went down on.
According to the charts its gone from 81bhp at the rear wheel to 100bhp, with similar improvements on the torque. There was always a bit of a hesitation at about 4000rpm when you accelerated this has now gone. It coincided with a sharp dip in the torque curve at this rpm on the graph which has now been removed.
All in all, I could be imagining it (he said, to appease the nay sayers) but i believe there has been an improvement.