How does using CiviCRM compare to using NationBuilder?
never used it directly, but had some customers that switched between civi and nationbuilder, in one direction or the other.

so the thing they liked better on nationbuilder was as well the thing they liked less: the ui is more polished, but/because you can do less. less features, less customisation, so easier to use and maintain.

a friend working for a political party that used it for all their candidates in the latest election said that the integration with social media- eg. from an email address being able to know the twitter or facebook accounts and how many followers and friends was quite nifty... but not always working as well as they hoped.

not sure how your extension compares to that, you're using the same base as they are, aren't you?