I had problems with the tech side. If you are not familiar with IM, there is a risk of you deleting the agents, as I did, which breaks the whole thing and required their assistance - which they promptly provided.
Also, had some problems with messages not arriving, though that could have been a legacy of what I mentioned above.
Other than that, I think the plugin is pretty good with the ($4.50 p/m) premium account. But the free account means the widget carries an ugly advert.