There have been numerous reports of issues with the old integration script (for VB 3.5, VB 3.6) not working on VB 3.7, hence the new release.
If you're using an older release, the biggest advantage you'll notice is that the plugin now ties directly in to your vBulletin usergroup permissions. So, no more editing a chat_global.php file, instead you just click over to the Usergroup manager to specify the AddonChat privileges for each of your usergroups. There are over twenty-five different options, so there is also much finer user-permission control in this release as well.
If you're using the Pro edition, I'd suggest either going to the Pro+ edition, or getting the remote auth. module to take advantage of this.
This script also doesn't require any template modifications as the previous release did -- so installation is very fast, and it can be uninstalled easily as well without having to edit any styles/templates.
There are lots of other improvements as well, including full UTF-8 support, and a smarter Who's Chatting system.
If you're running VB 3.7 and AddonChat, I strongly recommend using this product.