I'm pretty sure that having NSO in da house would be beneficial if the customer has already heterogeneous (i.e. spanning multiple type devices, routers/switches/firewalls, and multiple DCs) services deployed with NSO. Then having service logic already described, with ACI NED, transition to the new ACI construct model should be much simpler. I haven't used ACI NED yet, however I have dealt with brownfield-to-ACI migration by reverse engineering individual device configs, and I wished I have had NSO there. That was fun as hell.