First of all thank you for this plugin! I have been searching for something like this for the past couple of weeks.
I did some test and found out that it is not working properly on WP 3.3.1.
The 'Add New Limit' link is not working. I clicked on it and nothing happened. I'm stuck with the default setting.
As a user (contributor) I can still create unlimited post (pending for review). But once the pending job was approved I can no longer create new post (which is great).
I hope you can find time to fix the issues I encountered.
Thank you again for this plugin!