Recently there has been a ton of interest in the Hyper-V N1k running on Nutanix. This post goes through what is needed to get this working. For a general Hyper-V quickstart guide check out this Cisco doc. I wrote it during my time as TAC engineer there, and it covers most of what you need to know (some things changed in 2012R2 but the general post is there).
In a nutshell, the Nexus 1000v is a virtual switch that replaces the default switch in Hyper-V or ESXi. It utilizes a NXOS base (the same code that makes the Nexus product line work) and gives switching teams a familiar view in to the virtualized environment. You also get the benefits of logical switches (namely unified configuration across your hosts).
In a nutshell, the Nexus 1000v is a virtual switch that replaces the default switch in Hyper-V or ESXi. It utilizes a NXOS base (the same code that makes the Nexus product line work) and gives switching teams a familiar view in to the virtualized environment. You also get the benefits of logical switches (namely unified configuration across your hosts).