I bought this car used in January, and I have been extremely happy with it! I can honestly say that it has exceeded my expectations. I regularly got around 38-42 mpg during the huge Cleveland snowstorms we had in February, and that was even with letting my car run idle for 10-15 minutes to heat it up and get all the snow off. The ABS was a godsend in those storms too. I love how solid and roomy it feels for an economy car. I did test drive the non "S" version, and the doors didn't feel as solid, which is what prompted me to go with the "S". I live in an apartment and have to park on the street, so it's easy maneuverability and folding side mirrors are great too.
Aux jack, great fuel economy, center cluster, decent sound system, the folding side mirrors, the cold weather package, cruise control, tight handling, and ABS. Also, the seats are comfortable and adjust to accommodate both my short stature and my fiance's taller stature. It's also just plain cute.
It would be nice to have just a bit more storage. My mom has a 2001 Echo (the Yaris' predecessor), and there are a lot more storage compartments in hers compared to my Yaris. Also, I have the polar white with beige interior, and it's always a little dirty, even if it was just washed and vacuumed.