My car has 125000 and I still LOVE the Z4 after 5 years. It is comfortable, has good gas mileage (31 mpg on highway) even though I am low to the ground, I feel safe on the rainy, winding roads. The only problem I have ever had is not mechanical, the front skirt is so low to the ground that I had to change it twice because it broke. It is so reliable and fun to drive that I will drive it until the end!
Glass rear window, I have driven a Z3 and being able to see thru is a major improvement! And the roof but I really like everything about this car.