[Alfa1]

Yeah, you are right. I will explain why this is a big thing.

XMPP is a chat network protocol, also called Jabber.
Google Talk, Facebook talk and a bunch of other IM networks are XMPP.

A chat solution that connects to XMPP is basically your own IM network.
XMPP will allow your members to connect to your chat network through:
- IM messengers
- desktop client
- browser plugins

Effectively this means that you can keep contact with your members even when they are not on your site. And then all it takes is a notification or a chat from another member to pull them back onto your site.

Another interesting aspect of XMPP is that its performance is good. Its not without reason that facebook, google and other giants use this.

And off course you can connect your chat to facebook chat, google chat, etc. Which may be of interest as well.

AJAX PUSH Engine or APE is an awesome engine to PUSH real time data to browsers or devices. Think about mobile PUSH notifications that everyone wants so desperately for their mobile apps. This engine allows Cometchat to connect to basically anything without inevitably crashing your website.
When I say basically anything I mean mobile phones, tablets, gaming consoles, browsers, desktops.
More information here: http://www.ape-project.org/ajax-push.html

For APE you need your own server or VPS. But its also possible to use a hosted chat solution. Almost every chat provider offers this.

--------------- Added 23 Oct 2012 at 11:36 ---------------

Regarding Pro Chat Rooms:
despite several requests for information about their product features, I received no answer from them in years. I had sent them specific questions which are important to vbulletin webmasters.

After trying again this week I received several rude responses, which in the end left me without any answers. I am not sure if this is consistent with their general support attitude, but if it is, then Pro Chat Rooms is to be avoided IMO.