+ Supports Joomla! 2.5 native & Virtuemart 2.0
+ Supports browsers: IE7+, FireFox, Chrome, Safari, Opera
+ Meet Joomla! 2.5 requirements
+ PHP safemode off
+ Virtuemart configuration option “Enable Joomla Plugin” is checked.
If you are not using the default Virtuemart 2.0 template (use a third-party Virtuemart template), the extension will supports position: "After the description" ("Before the review area") and you need make sure the template supports plugin event afterDisplayContent.
See this post to know how to check whether your VM template supports above event or not and how to fix it.