That's one of the bigger advantages, definitely.
There's also a benefit in that Jabber is the first time someone has tried to make instant messaging an open Internet standard, like email or HTML.
The advantage to this is that you're not placing all of your eggs in a proprietary network run by a single company - this keeps competition going, and gives you the ability to change providers without having to change your instant message 'ID'.
Also, while there are a number of 3rd party instant messaging clients that communicate with AIM, ICQ, MSN, etc., they are usually based around a closed, proprietary protocol - this means that those networks can make minor changes to break the existing clients, bar them from connecting to their networks, obfuscate protocols so that they can't support new features, etc. Jabber is entirely open, so anyone who wants to make a Jabber client will have all the information they need to make a good one.
History has shown that the most ubiquitous and universal Internet protocols/standards are those that are open. Jabber is pretty small right now, but we wanted to support it before the rest of the web hosting industry even noticed it (as far as we know, we are the very first web hosting company to support instant messaging 'at' the customer's domain).
- Jeff @ DreamHost
- DH Discussion Forum Admin