I've been looking for a chat solution for some time now that (1) looks good, (2) runs fast, (3) will please users, and (4) doesn't require Flash, so can be used on a smartphone.
Blastchat is a great component/module/plugin pack, once you're set up its very easy to work out and runs itself. I had a small 'bug', which I went to the forum to fix, the admin/developer saw my post within 20 mins, asked me for a URL, and come joined me on my site!
He diagnosed my version was out of date in seconds, and hung around whilst I updated it. This fixed the problem instantly, and my users DIDN'T EVEN LOSE THE CONNECTION whilst it updated!! Just a refresh, away we go.
I cannot thank him enough, and cannot recommend it enough.
One thing I'd LOVE to see - an IRC connector so we could self host! That would ROCK. Oh and an iPhone skin!
Give it a try, you won't regret it.