Minimally functional

The only thing this plugin can do is let people complete a bare-bones form and either send you an email with their contact info, and/or dump a record into your ConstantContact account.
But if you have any custom fields, it won’t work. It lets you set up custom fields, but they won’t sync with the same custom fields you’ve set up in ConstantContact.
It’s also unreliable, and seems to fail to add records to ConstantContact without rhyme or reason.
It’s better to just insert a hyperlink within WordPress to your ConstantContact web signup form. Save yourself the hassle.