They should honor the deal, and I would have walked away. However, there is the mentality that "you own your beliefs" (psychology). Which is fine, esp. for an M3. Congrats on your new ride

Another example of bad dealer service: My uncle in NYC wants a Gray/Gray lthr '08 Acura MDX. The dealer offered to dealer-swap one within last month, since they did not have his choice in stock. He had put down a whopping $3000 deposit. Meanwhile, they keep pushing my uncle to opt for an in-stock vehicle that's a different color and/or has more options. At this point, its been over a month, and the dealer still has not gotten the vehicle. We're telling him to take his (hefty) deposit back and to go elsewhere.