I'm getting solid mileage on my commute, which is about 20 miles each way. I also have access to a Level 2 charger at my office garage.
(Note that weekend driving, when I'm making multiple short trips, is a totally different issue. The battery just doesn't charge fast enough to be viable for typical weekend driving with multiple short trips. I just ignore the battery and use it as a regular X5 on the weekends.)