Very complete, it allow to build custom forms quite easily. My personal favorite: the template system. It allow you to create different templates, then specify customs fields per template and finally, set a layout per template of how it is displayed in the front-end. My second favorite: the versioning. You can set some basic workflow rules for content approbation, which is very useful in a intranet for example. And lastly, I must say that the support from the forum is very efficient and quick. So far, the couple of comments and questions I had have been answered within a day.