SPD Custom Activities are an add-on many people use because they add new custom activities and conditions that can be used in SharePoint Design workflows. SPD Custom Activities give designers the ability to create more complex and powerful workflows without having to know code or use Visual Studio for development. Check out a list of the activities and descriptions here.
These activities have many benefits for users including:
- Make the automation of business processes easier
- Easier to build complex applications without the help of a (costly) developer.
- More power in the hands of the user
- Can quickly prototype, test and deliver applications
- Easier to manage and make changes to applications in production
On the other hand I feel it is important to consider the SPD Custom Activities from a governance and management standpoint. If you are responsible for managing and supporting the SharePoint environment its important to consider not only how these types of solutions will help the user but how will they affect the stability of your environment?