Class::DBI makes database-intensive projects seem causal. It creates a neat wrapper around a database record, allowing you to maniplulate your database in an object-oriented way. Relationships between tables can be mapped in your objects, making it easy to get things done.
There are some limitations and a bit of awkwardness when doing complex sql. If your needs are fairly simple, and your complex joins are few, then this is worth checking out. It especially works well in a templated enviroment (like HTML::Mason) where you don't want to see SQL in Perl in HTML. Class::DBI helps make your code more readable.
Over the last couple of years, Class::DBI has continued to evolve into a mature set of tools. Be sure to check out triggers, inflate/deflate, and data validation.