My Boxster is a Daily Driver, it does great in rain, snow and ice with proper tires. I enjoy ever moment I drive it and it makes a great DD. It sounds like it would fit your criteria, and probably costs about the same to maintain as a BMW. If you frequently drive in snow I might consider something else, but as regular all around car it is the ultimate daily driver with two relatively large trunks, and about as practical as you can get in a convertible.
