I don't know how many people use Jabber, but when I first tried it it was pretty confusing (I figured it out 2nd time trying it, but IMO it should be a lot easi

I don't know how many people use Jabber, but when I first tried it it was pretty confusing (I figured it out 2nd time trying it, but IMO it should be a lot easier), so I imagine for a normal user it might be confusing to start using Jabber too. As for your own IM client, users might be reluctant to download a new one unless there is a really good reason to download it (and to start it up each time you start the computer). If there is no good reason to be on it, then they might not. But you said that they'll have motivation to use it so I guess it should be fine. But if the motivation is that their friends are also using it, then getting their friends to use it too might be a problem.