DAO framework and SQL Maps framework are different things. You can use both, or either one by itself.
DAO is an abstraction layer that sits between your persistence solution and your service/domain layer. It serves to maintain a consistent API and transaction management facility to all of the higher layers (like service and domain). Without it, you will end up with various different types of artifacts from your persistence solution (like Session, or Connection) all mixed together. You'll also find yourself more tied to your persistence solution. One point about DAO – don't be afraid to write your own DAO! iBATIS is one implementation, but of anything else in iBATIS, DAO is the part that's is often best written for your specific application and customized to your needs.
SQL Maps is a persistence solution that allows you to easily map SQL to java objects. It is NOT an object-relational mapping tool, but can be used to map tables to objects using SQL.