The most obvious benefit of OSS is that it provides you free use of the code from OSS projects: you can include the code (with or without modifications) in your own project (however, if the code has a copyleft license it will require that your project be released as OSS as well). In some ways, this is like very large scale object orientation, where large chunks of code can be reused, leaving you to concentrate on new features or algorithms instead of reinventing the wheel to cover basic functionality.