Power BI has rapidly become the core of the Microsoft BI stack and add it's own new and exciting features such as collaboration. On-line and in-house BI servers are available.
Most BI journeys start with Excel, Power BI give you access to the features of your existing workbooks
Enterprise reporting in SQL Server Reporting Services can be incorporated into Power BI on-line and in-house services
Your existing data sources and more can be incorporated into your BI solution
Power BI has these components
The great thing about Power BI is that you can start with the Power BI desktop which is free! Power BI DownLoad and Pricing
Another aspect of Power BI is that new features are being added to Power BI on a monthly basis and there is a highly involved business and BI community committed to this product.