The BMW Z4 M40i is a deeply satisfying roadster that strikes an appealing balance between genuine performance and everyday usability. The turbocharged inline-six is one of the finest engines in production -- silky smooth, responsive, and capable of a glorious soundtrack when pushed. The 3.9-second sprint to 60 mph puts it firmly in sports car territory, and the rear-wheel-drive chassis provides engaging handling with progressive, predictable limits. The soft-top mechanism is quick and well-insulated, and the cabin is well-appointed with BMW's latest tech. Where the Z4 falls slightly short is in steering feel, which lacks the tactile feedback of the best roadsters, and in the ride quality, which can be unsettled over imperfections. The absence of a manual transmission option is a recurring BMW frustration. It also faces intense competition from the Porsche 718 Boxster, which offers sharper dynamics, and the less powerful but more characterful Mazda MX-5. As a comfortable, fast, and well-rounded roadster for spirited driving and top-down touring, the Z4 M40i is an excellent choice.