I have owned two 03 2.5 Z4s. One manual and one with automatic. Both have been excellent road cars and just a thrill in the hills. Change to the automatic was for the wife's desire. The automatic with the sequential manual shift works well and in general the automatic is easier in busy traffic. Both vehicles have been outstanding from a maintenance standpoint which includes excellent support from the dealer. While I would agree that the 3.0 would provide some extra horsepower, once you get the 2.5 rolling it delivers pretty well. Gas mileage (though not a concern) has been satisfactory electric top works great and once seated is quite comfortable. Only gripe is low top when getting in
Automatic top, sequential manual and great handling.
A little more headroom when getting in and out when top is up. About an inch would do it.