Nexus OS

Nexus OS by Cisco look to be OK and is used in a lot of data centers

it is different in configuration to the classical Cisco IOS whereby you have to enable features that you what to use, below are the features of a nexus 7K

switch(config)# feature
bfd                     lisp                    privilege
bgp                     lldp                    ptp
bulkstat                msdp                    rip
cable-management        msrp                    scheduler
cts                     mvrp                    scp-server
dhcp                    netflow                 sftp-server
dot1x                   ngoam                   sla
eigrp                   ntp                     ssh
ethernet-link-oam       nv                      tacacs+
evb                     nxapi                   telnet
evc                     ospf                    tunnel
evmed                   ospfv3                  udld
fabric                  otv                     vmtracker
glbp                    password                vn-segment-vlan-based
hsrp                    pbr                     vni
imp                     pim                     vpc
interface-vlan          pim6                    vrrp
isis                    pong                    vrrpv3
lacp                    port-security           vtp
ldap                    private-vlan            wccp

with some of the bigger switches, you can actually run docker images on them which I think could be quite interesting for distributed monitoring using a Zabbix proxy on the switch will have to look at that another day