LaTeX and/or MathML would be killer in evernote. Most hardcore math users (scientists, students, teachers...) would probably opt for LaTeX because the expressions are much (MUCH) shorter than MathML, but one could argue either way. But having math, real math in notes is central to people who use math. As for implementation, don't reinvent the wheel. Check out mathjax (http://www.mathjax.org/). Open source. JavaScript. Handles LaTeX or MathML and interprets it to html for webservers. Even available as a WordPress plugin. The heavy lifting is done. You run it on your server, it reads the math codes between your delimiters, it spits back inline images of the math. Loverly. You can leave the actual creation of the codes to the user. If they are sophisticated users, they just type in the codes as they go. If they are writing complex expressions with unfamiliar math or are more casual users they use any of the many good button oriented editors available free or for fair fees. Or dump the codes out of their favorite math programs. Could happen. Really could... Getting off my soapbox now. Thanks for listening.