Yeah, the 6-speed ZF on the diesel works quickly and smoothly 85% of the time. The other times, it holds onto gears too long on non-existant uphills and when the engine is cold. And occasionally after making a turn, it'll stumble in too high a gear and require a few seconds and some abrupt downshifting to get going again.

I've sampled the 8-speed ZF in the X3 and that's brilliant.