The ease of use, it's very intuitive for anyone with basic computer skills (like me).
I can't think about anything that would make us not want this product! It has been extremely helpful when we need our customers' information but don't know how they are going to get hold of them or if their email address even exists anymore - now all these things have become so easy thanks to optin sight!! Not much at present as everything runs smoothly without any issues/complaints from myself nor my colleagues who also uses the system daily.