Well it has the best fuel efficiency of any regular gasoline engine car...
33 city and 41 highway. A Focus is 24/33. Estimated annual fuel cost of the smart is $897, for the Focus $1,060.
The smart starts at $12k. Focus at $15k.
Sure, the Focus is a lot more of a car, but the smart really isn't bad at all for a secondary daily driver. I think it's sort of an icon for some people too, like having an iPod. The Zune has more features, but the iPod is "cooler".