The Yaris may look very small, but it actually has more interior room than the Toyota Corolla.
The trim levels on the Yaris in the United States are the convenience, power, and all weather guard. These are the same as the CE, LE, and RS packages that are sold in the Canadian market. The Yaris Sedan also is sold as the Yaris S, which comes with the standard features on the convenience package. With the power package, alloy wheel are an option.
One drawback on new Yaris' is the lack of standard curtain airbags. These are standard features on the competition, and surely something that Toyota will include as standard in the future.
Along with a low retail price, the Yaris also gets very good fuel economy. It gets about 40 mpg on the highway and 34 mpg in the city. Those are both very good numbers for a gasoline car at this time (I expect much better in a decade or so).
The first Yaris' are starting to hit the used car market as they come off lease. You might not expect a lot of these to hit the used market right away, but remember that a lot of people who buy them new can't afford to buy a new car and end up losing them to the repo men. You can pick them up for cheap on places like eBay.