I'm surprised I didn't review these tires earlier, but at any rate it's a good time.
We just wore them out.
Some tires just seem to work spectacularly well in certain applications, and in this case it's our old (1998, 180K mile) E39 540i. The RE760s felt great the day they went on (December '09), and they feel great at the wear bars. They've worn evenly, they haven't gotten particularly noisy or harsh as they've aged, and we've topped 30K miles in treadlife which I consider to be very good. Maybe not an optimum rain tire, but good enough.
So I just ordered another set.