今更だけどRails4.2のchangelogを眺めていたら見つけた嬉しいモノ(試してない)

Take label values into account when doing I18n lookups for model attributes.

The following:

# form.html.erb
<%= form_for @post do |f| %>
  <%= f.label :type, value: "long" %>
<% end %>

# en.yml
en:
  activerecord:
    attributes:
      post/long: "Long-form Post"

Used to simply return "long", but now it will return "Long-form Post".