Not on the Z4 for me.
However earlier this week a mint Z3 Sterling grey with roof down passed me (mature male driver)
That had chrome roll bars and it suited it to a T.
I rather like them but crazy money ! Don't think the pictures help sell them though bet they look loads better with a set of sports seats. Think the colour of the car could also be a factor in how they look. If they were cheaper I would be tempted.