When the Z4 came out to replace the Z3, I thought they ruined the idea. It's a much different car and when you drive it, you can forget about the Z3. The lines on the car all seem to fit and have purpose, even though I'm not a fan of the Bangle designs. I bought the Z4 3.0si convertible which is a fast car and looks unbelievable with the sport package and 18" wheels. The sport package completely changes the look and driving of the car, it's a must. It's fast enough even with the auto trans which has the paddle shifters. The extended leather and premium M seats are a must too. All the options raise the price, but if you're seriously considering this car, cost is not a concern.
Just about everything on the car really. The lines of the design are great. People stare at the car as if it cost twice what it did. Out performs 95% of the cars you'll pass. Interior makes the most out of the space the car has, quiet even at 75 with the top down. The Sport package is a must!
Ditch the electric steering, it feels on/off, either too much or no boost. The Z4 M is much more natural feeling. I know the cup holders are an afterthought and they're useless. The silver plastic on the steering wheel is completely out of place on this car, use aluminum or other.