Dell recently published an interesting piece on how F5's BIG-IP and ARX address some of the key challenges people encounter when they embrace server virtualization.  The challenges they discuss are:

1. Resource Starvation
2. Lack of Application Awareness
3. Unanticipated Costs
4. Unused Virtualization Features
5. Increased Storage Requirements
6. Congested Storage Network
7. Management Complexity

The article From Dell's Power Solutions can be found here.