Doing some googling for the coming NX-OS 5.1(3)N1(1) for Nexus 5000 I found this:
Cisco NX-OS Software Release 5.1(3)N1(1) for Cisco Nexus 5000 Series Switches and 2000 Series Fabric Extenders: https://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/product_bulletin_c25-686744.pdf
Update: The same document in HTML: http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/product_bulletin_c25-686744.html
Yes there are the goodies like FabricPath and Adapter FEX and PTP, but who cares about those anyway 😉
For me the best feature that is promised is dual-layer vPC. It means that it will be possible to dual-home FEXes to two Nexus 5000s (= vPC between the FEX and two Nexus 5000s) and still connect the end-hosts to two different FEXes with vPC (= vPC between the end-host and two FEXes).
I should probably insert here some picture of the topology but hey, all the fancy Nexus-blue topology diagrams look eventually the same, the port-channel indicators and various straight lines are just connected a bit differently in each topology, so…
There are still plenty of servers having only one NIC connected to f.ex. backup network so dual-homing FEXes is a kind of must in some implementations. Currently (as of 5.0(3)N2(2a)), dual-homing a FEX prevents connecting end-hosts with vPC so you must use the traditional active-standby teaming on the teamed NICs on the servers.
Also, the number of FEXes is limited on Nexus 5000 (see the configuration limits in http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/configuration_limits/limits_503/nexus_5000_config_limits_503_n2_1.html) so you really must think before deploying FEXes in both single-homed and dual-homed topologies on the same Nexus 5000 switches.
With this new dual-layer vPC feature you can presumably start replacing the active-standby teaming configurations with LACP teaming (port-channels) to get both NICs transmitting and receiving on the servers and still get the Nexus 5000 redundancy for the single-connected networks or servers.
Hopefully the sequential port-channel hashing operations will result in balanced traffic distribution and not lead always to the same Nexus 5000 upstream of the servers 🙂