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.