The seats are comfortable and highly adjustable, but sit high enough in the cabin that taller drivers will find the low windshield header problematic. With the top up, headroom can be tight as well, though only for those well over six feet in height.
Despite the dearth of space, there are a fair amount of cargo nooks in the Z4's cabin, including a small cargo shelf behind the seats, a low cargo net to trap objects, clamshell door pockets, and a center console tray. Adding the cold-weather package also brings seatback netting, luggage straps, and a storage box at the bulkhead.
In the trunk, there's space for a couple of carry-on size suitcases, but not much more.
As for fit, finish, and materials, the 2012 Z4 lives up to BMW's high standards, with quality aluminum, wood, and leather trim and upholstery; an extended leather option that covers the dash, door caps and visors; and generally excellent panel fit. Squeaks, rattles, and vibration--a frequent issue in open-top cars--are minimal, and BMW even takes an extra step or two with features like Sun Reflective Technology in the leather seats, which keeps them from reaching scorching-hot temperatures even when exposed to direct summer sun.
Wind, road, and engine noise are generally low, especially with the top up, though the growl of any of the engines will permeate the cabin in more aggressive driving--as it should.