This started out as a review of the "Warlord Optin" plugin ... but quickly turned into a (hopefully;-) useful case-study on providing value.
The big take-away: the old model of getting optins (first get the optin, then lead subscribers through a 'nurturing' campaign that shows them how 'valuable' your content is) is pretty much doomed.
End-result: you get a lot of fake email addresses, and low engagement along with it.
A much better way is to lead with value so people end up giving you their REAL email address in the first place, and look forward to engaging with your emails/content.
Meaning: if you do know how to provide value, but you're not getting subscribers (who could then check out your great content, and the fact that you are trustworthy), then the Warlord Optin plugin is definitely worth testing.
But, if you do NOT know how to provide value (yet;-), then don't bother with the optin plugin ... it would simply be an attempt to 'trick' people into signing up to your list ... and the moment they're on that list, they'll realize they've been tricked, and unsubscribe/ignore/hit the spam button.
As I mention in the video, if you are trying to figure out how/in what niche to provide value, then check out this FB-post here.
Either way, watch this video which has a nice lil' case-study illustrating the points above