I used to work at a BMW dealership for a good amount of time (not a salesman so no flaming please). I have driven all the Z4 models...2.5, 3.0, 3.0i, 3.0si. I must say the 2.5 sucked...the 3.0 was alot of fun with a stick. As far as the new ones go...the 3.0i is alot of fun (comparable with the old 3.0 model) with a stick and has plenty of power. The 3.0si has even more (almost unneeded hp).

A must is the sport pkg...I see you have the m-contour seats on the one you are looking at, also a plus. Most of the 3.0si have prem and cold weather pkgs.

I would recommend you lease it b/c of the high residual...lower payments(bmw has some of the highest in the market) and when the warranty runs out, although the z4 does not have too many problems, BMW's are VERY expensive to maintain and repair. Plus you will want a new one anyway.