Pro Developers can create their own plugins
Developers can also create their own Yeoman generator which are practically plugins with which Yeoman works. Generators are basically Node.js modules and can be created just like any other Node module.
There is also a very detailed and useful guide on how to create a generator on the Yeoman official website.
Pro Huge number of generators for scaffolding your project
Yeoman generators allow you to quickly set up a new project. Invoked with the scaffolding tool 'yo' they provide a boilerplate & tooling selection. There are over 1000 generators, including generators for ember, angular & backbone, to choose from, the majority of which are community maintained.
Con Combining Yeoman and backend frameworks can bring problems
Combining Yeoman and a backend framework such as Django, Rails or Laravel can create problem because the project structure of Yeoman may not be compatible with that of the backend project. It can be tuned to work but for small projects it can be relatively time consuming.