Hi,
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.
<script type="text/x-mathjax-config">
MathJax.Hub.Config({
"HTML-CSS": {
scale: 85
}
});</script>
<script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=default"></script>
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?