None that I can think of
The service itself is totally overpriced for what it is. Perhaps the email follow up feature could be useful, but not at that price.
I signed up for a trial of NinjaOutreach. Tried it briefly, decided I might possibly come back to look at it later. After a couple of weeks I realised that they had billed me $594 without any warning. I didn't even get any trial ending soon emails. Nothing. When I complained they told me that they have a no refund policy and it was basically my problem. Then they offered a partial refund of $297 take it or leave it and then went silent. A totally unethical company. I'll be sure to complain to the Better Business Bureau and to leave a comment on any future mentions of them that I see online.