We've been using this for a fair amount of time now (>2 months) and my ultimate conclusion is that this is, at best, a buggy Beta product.
* Private group chats do not remember member permissions, if you so much as tab to another conversation you have to re-enter the group password EVERY SINGLE TIME. Which is absurd functionality if you need/want private group chats.
* Private group chats cannot be hidden - in fairness this is pretty clear on their Demo site.
* The push server is an extra $9/month, but it consistently
- Drops messages
- Sends phantom alerts
- Becomes unstable and does not send messages in consecutive order, distorting the order of the conversation
So yeah the push servers, which are marketed on the ArrowChat site as a way to decrease your server load, are not stable enough IME.
Of all the add-ons I've purchased for my XF install this is far and away the least polished. I'm sure its alright if the features you use don't happen to fall into the almost completely broken portion of the add-on, but if those are the functions you need (especially private group chats), don't bother with this add-on.