I love Optin Revolution. I can't wait to see what comes out in the pro version.
I would recommend it for many reasons:
1. MANY great & easy to follow vid tutorials!
2. Versatility to add just about anything you want to pop-up
4. Integration of several email apps.
5. Fabulous, thorough and QUICK customer support via email.
6. The little blue guy who hosts intros the tutorials.
Totally recommend this plug in.