Ran into 2 issues.
1. when I installed it the folder created was mediacore-wp-plugin which caused a number of js errors for missing files as the plugin is looking for a folder called mediacore. I simply renamed the plugin folder and this solved the issue.
*There are functions you can use in WP where you do not have to hardcode in the name of your plugin folder which would have solved the problem to begin with. I don't have the snippet handy right now, but will post it when I do.
2. When I activate the plugin then the visual editor breaks. I see no buttons in the visual editor when creating or editing a post.
Deactivating the plugin solves the problem... which of course is not really a solution.
***Turns out it is something in WordPress 3.4 breaking the plugin. My demo of 3.3.1 works just fine. Would be nice to have a fix though as all my production sites run trunk.