I have had my Z4 since November and normally drive it on weekends. My everyday vehicle is a 4Runner.
I can see where if one drove the Z every day one could get used to the understeer of the electrical assist. But it feels sluggish to me and I think could contribute to accidents. That almost happened to me. I came into a corner a little hot, I turned the wheel and then had to quickly compensate for the understeer. I hate to say it but the 4Runner is more responsive.
I don't know why they had to mess with something that worked. Maybe adding tower braces will help.