An old co-worker of mine from a decade ago had one of the original Smart For-Two's. I took a ride in it, and remember thinking that the automated manual was an absolute POS. The diesel motor wasn't great either.
The ONLY thing it had going for it was it's quirkiness. It was cool in a special kind of way. I don't think it was much more fuel efficient than a Yaris, either, and given the Yaris' cheaper price, better driving experience, and better practicality, you would really really have to want to be quirky to buy a Smart.