BMW's hot Z4 Roadster receives a major makeover this year with improved engines, updated styling and more luxury features. The 2.5i becomes the 3.0i, while the old 3.0i is reborn as the 3.0si. The Z4's drop-dead good looks are bolstered by its impressive performance abilities and affordable price tag. With equally-matched competitors from Audi, Porsche and Mercedes-Benz, it would seem the Z4 should have to fight for every sale. Yet Americans appear to love this car and BMW dealers continue to sell every one they get their hands on, which may make it difficult to drive a hard deal at purchase time.