WAN Optimizers for the data center

Gartner just released their Magic Quadrant for WAN optimizers where they point to the emergence of data center-centric WAN optimization.

Silver Peak has talked about this for some time now and indeed Gartner noted that they were a leader in the space (along with Riverbed and F5. My question is what do you think are they key criteria for a data center class WAN optimizer?

BTW, the Gartner report can be downloaded from here: http://www.silver-peak.com/landing/gartnerMQ/