With how Intervals currently works project milestones are akin to a sprint and the milestone’s graph tab can be used to view a burn down / burn up type of view based on the status of the tasks. Intervals is designed in a fashion that does not include traditional task dependencies like the waterfall method and MS Project utilizes (Finish to Finish, Start to Start, lag, lead, etc.) and Intervals is built more around Agile project management philosophies (http://en.wikipedia.org/wiki/Agile_software_development) where tasks are more free form in nature and milestones are utilized heavily.
The project milestones feature does have quasi dependencies if you need to shuffle your project around. Say for example there is a design milestone that ends the first phase of a project and it runs late. You can move the due date of the first milestone and all of the other milestones and tasks will move as well. If you are unfamilar with using milestones in project management this video introduction might be worth a look. If you are interested in seeing each project and the milestones in a Gantt chart like display the Periscope report might be worth a look.