This machine's main selling point is versatility. Lecturer can face audience while writing.
Colored pens look good for text and simple diagrams.
Legibility of on-the spot writing is often worse than with chalkboard. Needs too much projection range to be practical in a small classroom. The lecturer's body often obstructs the audience's view of the screen. It's easy to misjudge type size, leading to eye-squeezingly tiny text. Use no more than 7-10 lines of text, and make it big.