I had them on my previous XJ. Never really cared for them, but didn't hate them enough to take them off. If it's cold out a slight knock with a branch will shatter them.
One thing I really disliked, was how they blocked my hand rest location. When it's hot out, I always have my arm out the window. Elbow resting on the window sill, and fingers resting in the rain gutter. With these, I couldn't do that.