Improve development with milestones

The team which I'm member of works in a month long iterations. We often have to develop quite large user stories. To improve our development process we introduced the idea of milestones.
How to define the milestones:

1. Define about 3-4 milestones (for a month long iteration).
2. Each milestone must deliver a testable set of functionality.
3. One milestone can comprise tasks from more than one story.

It gives the following benefits:

1. Early testing - as the milestone is delivered the QA team can start doing its work.
2. Better feeling about the progress of the project (besides the burn-down chart).
3. Smaller goals are easier to achieve.

Of course the idea of milestones is not new. See more at wikipedia