i just leased one (see Numark318i) and ill tell you its a very fun, fast car to drive, and still hasnt been broken in yet, so i havent unleased it past the 4500rpm...but for the power it has untill that spot is still amazing. the blind spot i dont care for, but you get used to it after a week, and the copholders are nice, but arent the most secure, unless you manufacture some clip on thing for the bottom of them. but the handling on this thing just blows me away...i hit a 20mph off ramp at about 55 which wasnt the smartest idea, and the car broke loose, but the DSC system kicked in an corrected everything...kind of crazy how well those systems work. the car also feels safe in a weird way, i think its mainly because you have that enormous hood in front of you, and although its still a roadster, this roadster is a little bigger than some, and by no means heavier, it just feels like it has way more crunch space in the case of an accident compaired to a z3, or a miata or a boxter...good stuff, amazing gas mileage, heated seats work very very good, and we managed to go camping with a tent, 2 sleeping bags, foldable air mattress, portable two burner gas grill, lots of clothes, and lots of food...so if you plan out your packing stragety in the trunk, you can acctually fit alot in there...it also an easy car to cruise in, as it doesnt really hike up through the mph on its own as alot of sports cars do...so its a breeze to crawl around town in. but my favorite thing about this car in my opinion would have to be that when you hit the turns and the top is down, it feels like im in a 70mph go-kart, it feels like you weigh two pounds...very nice feeling...look out lotus elise
so get that z4, its a great car...theres nothing to them, just pure roadster (unless you get that navigation crap...who needs that, its a convertable!)