Interesting thread. I'm in France at the moment and it seems that nearly all stations are selling only e85 95ron petrol or super 98. Have been using the e85 (in the 530i) and noticed that the car seemed to be a little sluggish. Filled the tank today, a little over half a tank, with 98 and the car felt much more like it ought to. It might just be my imagination, but certainly felt that way today on the last third of a 650km run.
As an aside, the e39 530i is a great mile munched in these conditions. In this case the double glazing and adjustability of the leccy sports seats made it a very refined high speed run. Got out at the end as fresh as a daisy.