Essential use cases dialogues capture the core requirements of each use case, but without getting into technological details. Because of this, they are short, quick to write, and easy to manage.
Essential use cases are smaller (and thus quicker to write, review, and modify) than longer, more detailed use cases (for example, the more traditional use cases used in the Rational Unified Process [10]).
However:
You still have to write them, which takes time and effort. Finding the ``correct'' level of abstraction in which to write a use case -- enough detail so that it makes sense, but not too much so that it determines the details of the interface design -- can be difficult, and so can take several attempts for some use cases.