your plugin seems not to work with WordPress 3.2.1. I'll post a little bug report about it later.
The other thing I don't like about it, is that it adds the following code to each page, no matter if it needs mathjax or not.
As I don't use MathJax on many pages, this is not necessary and makes WordPress slower.
Could you please configure your plugin in a way that MathJax is only added if it is used?