afaik, conf-d is not in erlang though, fwiw, it does have erlang bindings. most of the config of these 'boxen' happen via cli's by network administrators.

what conf-d/tail-f brings to the table is the distributed nature of 2-phase commit to device configuration, as well representation of operational and runtime states of these devices. which has some appeal to it.

source: have worked for csco quite a number of times :)

edit: slight clarification on conf-d capabilities.