honestly, after the first few tankfuls i can't get too interested in tracking MPG anymore. life is too short and there are too many other important things to me than losing sleep over minor weekly variances in estimated MPG averaged over the course of a tank and ~400 or so miles.
i sleep well knowing that it's at the top of the range for fuel efficiency short of a hybrid. i don't fall into the trap of making comparisons with other vehicles. claiming my xyz car gets 32 and my smart "only" gets 42 is a meaningless comparison IMHO.
lastly, i see in my bank statements that i am spending considerably less on fuel than i did with either of my two jeeps when driven on a consistent basis. tracking MPG on today's trip to work and comparing to yesterday's trip to work and the best trip to work and the worst trip to work is a bit too granular for me to get worked up about. i think some people could use a real dose of long-term perspective, and if they must make comparisons and find that another vehicle does better for their situation, then my recommendation would be to get our of their smart asap for as much profit as they can make and keep driving their whatever-other-car-that-outperforms-the-smart and quit the constant bellyaching.