AZC has switched from WP-LaTeX to MathJax. There was no real problem with WP-LaTeX, but MathJax offered some improvements:

- Improved rendering
- Local installation: MathJax can be installed on your own webserver, so that you're no longer reliant on external services
- Easier typing of LaTeX: in WP-LaTeX, you have to type the word LaTeX after the first dollar sign, and in MathJax you don't

Here is a before-and-after image (you'll have to click on it to view full size to see the difference properly):