There are a lot of good things, but I would like to mention 2:
- Querying is fast, faster that any other system. This is because EXADATA can execute the queries in the Storage itself! It saves a lot of time of sending and receiving files.
- Thanks to its power, you don't need different OLTP/OLAP database instances. They can work in same DB without performance issues at all
Mainly use for big data project and, in general, any project that needs to have databases with millions of rows.