Working on projects in groups encourages positive interdependence and interaction. Projects should be an anchor upon which to build learning. The many different takes and approaches to incorporating projects into the classroom are all equal because they accomplish the same goal. It is possible that project-based learning methods can support tried-and-true instructional strategies and teach curriculum equally well.
Projects can be the center of the learning where the authentic experience will guide students to learning whatever curriculum is in place without sacrificing "coverage" of content. Projects are a viable method of assessing learning. Unfortunately, some projects can simply amount to "busy work" for students or present more hurdles to learning than benefits. However, a good project can lead to meaningful learning without giving up the curriculum that needs to be taught.