I think this app lacks functionality vs. other referral apps. This app has no mechanism to introduce your existing customer base to the new referral program in one step. All this app does is send referral invitations AFTER someone completes a purchase. This greatly reduces the effectiveness of this app. If you launch a referral program, you want to do it with a big bang and sign-up as many of your existing customers as you can in one big campaign. This is where this app fails. I uninstalled it.
Edit 06/09/2018 1pm EDT: As soon as I posted this 1-star review, I got a vengeful email from ReferralBee telling me that they "report [our store] to Shopify and GDPR". Beware, these guys are acting in bad faith and don't shy away from libel and false allegations just get even with a 1-star reviewer. In my view these are very unethical and questionable tactics that have no place in the app store.