This is the software publisher’s description.
Messenger Plus! Live is an add-on for Windows Live Messenger from Microsoft. Messenger Plus! adds numerous features to Messenger to make it more enjoyable. Features include the ability to have a multi-chat within one window, by making use of tabs to control your chat – much like the tab function you’ll see in Mozilla Firefox. No need to open a new chat window.
If you a heavy-duty Messenger user, you can setup quick access texts so that you can create message shortcuts and the entire word is automatically extended by Messenger Plus. Messenger Plus is very customisable, so you can include your own sounds, images and colours for your setup.
Thought out end-to-end to improve and enhance your instant messaging without getting in your way, Plus! adds lots of capabilities to Windows Live Messenger. It lets you use them at your will from the simple Plus! menu that gets added to every Messenger window and a couple of new buttons you'll find within the Messenger interface.