I have been using it for a week already, and I can say that this app is AWESOME.
I have tried several chat apps both on AppSumo and from the others, and currently I am stick with Re:plain.

I like its simplicity, despite the setup that is quite different from the other similar apps.
This app is unique. You don't have to login to Re:plain's website to be able to respond to any message coming to your website. You only need your account on Facebook Messenger or Telegram. In this case I am using Telegram where I can manage the incoming chats from my customers. At first, I didn't think that it would be a smooth experience setting up this app as some people suggest on their reviews or questions here, but later on I am kind of understanding the philosophy (UX) of using this app, and honestly, IT IS NOT THAT COMPLICATED :-)

Although using Telegram is quite accomodative for now, but I do think Re:plain can make it more useful if there is a Dashboard for users to manage the incoming chats, and furthermore they can develop it more advanced if it has a CRM features. If that's available, other chat apps should be more concerned.

I give 5 tacos as a way to support the developer, to keep listening to us and develop the apps to fulfill our needs.

Cheers.