My brother has 330Ci convertible he drove it all winter in Toronto with soft top. No problems what so ever. It has sports package with all bells and wistles. Trust me it's a REALLY SWEET RIDE plus chicks dig it
I've been driving a Z3 in Chicago for the last couple of years so I know how it goes. Also my close relative recently bought a 325Ci so I have an idea what is a bigger chick-magnet Z3 or 3-series convertible (actually 3-series convertible more of a chicks' car). And you don't need to convince me on sweetness of BMWs, but sweetest drive of them all is M5 (E39), I got to drive it for some time on California highways.