About latehe (it is not latex, by the way) I'm not sure. Know him well enough, but the set of equations it is still somewhat slower than by hand. Besides, if You are not so evil as LaTeX-based WYSIWYG-editors, to compare written on the Board and You have on the laptop will be problematic, especially in the case of cumbersome formulas. And compiling each time and check the time, and if you make some small mistakes, a lot of time (relative to the speed of doing lectures).