The Idea is quite simple for this kind of component, so I will not give you a good rating for many reasons:

I didn't have big problem with the language, although I had to guess what every registration field meant. Sadly, nowadays one cannot publish a component for Joomla and try to distribute it worldwide in a french-only website requiring registration (I am not natural born english speaker, but it's the way to communicate to the whole world mates).

But that was not the problem. I don't usually write feedbacks here, but I know from my experience in joomla how frightening is for newbies to find out what happened to your joomla installation when you install a component and the frontend sends a blank page with an error... You can be really scared... So developers should check such a simple component is working perfect with the last versions of joomla in an updated server... Because I had to remove manually through FTP when the frontend gave me an error. Besides I couldn't see any NT component installed in my component dropdown in backend...

Go on with the work mates.

Very nice extension. Both free and pro versions.

It's the first one that I pay for and the first one I comment, and it's really cheap for the advantage it gives to my site.

Pros: Very easy to install, the pro version lets you control Ips, ban, censore words, use a captcha... Necessary things (sadly), due to the amount of spammers out there searching for every little space to write their crap on. I thought I wouldn't need security, but I did...
Tip: The languages are easy to change just by editing the en-GB mod-shoutbox.ini file.

To improve: The app would be perfect if it could be more customizable and sizeable through the admin panel, without the need of having to edit the .css file.

Congrats to the developer(s) for this easy and really useful app.

Blessgins