Hi,
Now a days solution manager is mandatory.  
1. it is used for generating keys and downloading support
packages 

2. it is used to document  user  requirements and preparing
scenarios what needs to to be adopted using solution
manager, where the blue print is the part of solution manager 

3. it is used for reporting, solution desk,to manage the
change requests and use to monitor entire landscape Central
message processing in the SAP Solution Manager:  

- Display customer data, problem description, priority,
attached documents, Service Level Agreements (SLA)
- Assign processor
- Send messages to the creator and other processors
- Forward message to other processors or support units
- Create documents and URLs
- Attach documents
- Status assignment and monitoring
- Create a worklist with selection conditions    
hope this would helpful to you.