Yes, it's quite unbelievable, yet true. Please look at the announcing blog post: Using the conceal Vim feature with LaTeX by the person responsible for MacVim. To give credit where credit's due: Vim, LaTeX and 'conceal' made me aware of this.

It basically gives you a preview, but not via a build using pdflatex or similar, it happens on the spot using Unicode. I'm not saying I will be using this feature often (I have yet to install Vim 7.3), but I feel this might be interesting when editing a document: when you're writing complex formulas you are aware of everything you're doing at that moment, but afterwards that knowledge is gone.