I also would love to have the ability to write formulae in Evernote, the website supports LaTex so it would be great if this could be implemented into the app(s). I write a lot of notes with formula in and currently use Microsoft word and then snipping tool in. Which is not ideal but is my current work around.
As a side note if you disagree with this request maybe just don't respond to this thread as it is not aimed at you. It is aimed at the Evernote devs.
\newcommand*{\qf}{$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$