The Z4 is not as agile as the Porsche Boxster or Honda S2000, largely because of its imprecise electric steering. The inline six-cylinder engines are impressive. The M roadster and coupe have a 330-hp, 3.2-liter engine and a conventional steering setup, which is much better. We tested the muscular 215-hp, 3.0-liter version. The ride is not punishing, though it is choppy. Fit and finish is very good, and the power-operated top is well-insulated and has an automatic latching system. Standard electronic stability control and traction control keep the Z4 secure.