I wouldn't trade my M3 for it (not even close), but I'd love a Z4 as a 3rd car, just to drive during the spring or take it to Charleston. It has to be one of the most beautiful cars BMW makes right now, along with the 4er Concept and the M6 in my opinion.
Current: 2008 BMW M3 Sparkling Graphite/Bamboo Beige/6MT. 1999 BMW M3 Techno Violet/Dove/5MT. Next: 2017 BMW M3 CP