I'm not sure why you say that, but having driven a couple of the ZF8HP's mated to BMW 4 cylinders, back-to-back with the X1, I just don't see much of a difference (longitudinal, haven't driven the new ZF sideways box in the newest X1's). Shift times seem very similar. Yes, the Aisin feels slightly softer during shifts--slightly...but as someone who hates automatic transmissions, I really like the Aisin 8 speed box in the X1.
I think a lot has to do with the programming. I've read a lot of complaints about this transmission among Volvo and Buick owners, and VW seemed to screw it up in the first Jettas... but the same is true of the ZF transmission. I drove one in a Jeep and thought it was the second worst transmission I ever drove, after the Focus DCT... Programming counts for lot.
It's definitely a component of the fuel economy--it's geared quite tall, and that matters at highway speeds. But it's not much different than my Golf R, which has tall gears and no torque converter...