VMware releases a new vSphere License for the hosting of VDI desktops. In addition to the new vSphere 5 licensing editions, VMware releases a new edition : vSphere Desktop : vSphere Edition to host Desktop Virtualization

vSphere Desktop is a new edition of vSphere for deploying desktop virtualization.  It provides the full range of features and functionalities of the vSphere Enterprise+ edition allowing you to achieve scalability, high availability and optimal performance for all of your desktop workloads.

Also, vSphere Desktop enables you to realize high virtual desktop consolidation ratios at a lower cost as it comes with unlimited vRAM entitlement. The vSphere Desktop edition is intended for customers who want to purchase only vSphere licenses to deploy desktop virtualization. In addition to the vSphere Desktop edition, VMware also sells a comprehensive end to end desktop and application virtualization solution – VMware View. 

vSphere Desktop is already included in the View Bundle – The desktop and application virtualization product from VMware. This offer gives customers the option to purchase vSphere Desktop as a standalone vSphere edition outside of the View Bundle.

vSphere Desktop is licensed based on the total number of Powered On Desktop Virtual Machines. It is available in a pack size of 100 desktop VM at a license list price of $6500 USD.

vSphere Desktop can be used only for hosting a VDI environment.

The article below also gives a good example on how this new edition impact licensing cost in contrast to vSphere Enterprise Plus license.

vSphere Desktop is the cost effective vSphere SKU for deploying desktop virtualization.

Example: Customer deploying 1000 Win 7 desktops

Assumptions:

Memory/VM =1 GB
vSphere Ent+: List Price: $3495/CPU with vRAM
entitlement of 48GB
vSphere Desktop: List Price $65/VM, Unlimited vRAM
entitlement for desktop VMs

# of vSphere Enterprise+ licenses required = (Total pooled vRAM required for all desktop VMs / MIN (vRAM used per processor, vRAM entitlement per processor)) = (1000 desktop VM *1GB / MIN (vRAM entitlement used,48GB) )

# of vSphere Desktop licenses required = # of desktop VMs

More information see this FAQ doucment over here.