Cisco support will certainly increase the attractiveness of Microsoft's Hyper-V environment (server virtualization) to corporate, enterprise clients.
As Microsoft positions their Hyper-V environment against VMware's ESXi, it will need to offer greater support and visibility of the managed environment. Cisco will be offering virtual switch support for Hyper-V, which is similar to what it offers VMware environments. Currently, the battle is being won by ESXi.