Using version 1.5 with a huge amount of plugins [on display at http://shadows.os42.com/index.php/areas/ and your plugin is working now. It is showing popularity and percentage on each post. The sidebar is also producing a list of the most popular.
A few issues though.
1. The Popularity plugin would not work properly until I deactivated the The Referraliser plugin @ http://nfo.zackdesign.biz/archives/plugins/395
2. I then noticed that when writing a post, the preview option at the bottom of a post now produces this error - You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 3
3. Consequently, I then tried to deactivate the Popularity plugin but this produced a result of no posts showing in main content. Sidebar and header still working as normal.
Apart from these issues, I really like the plugin. Could you advise though, as to how to apply styling to the produced Poularity % in the posts...
Hope this all makes sense..