Generally a pencil tool, though flexible is too hard to use and doesn't look good no matter how good you get at wielding it. I would likely not use the pencil tool for external communications - that would only suffice for internal explanations, not professional demos.
Pros:I like that all the tools-screencasting, video camera, markup and link sharing are all rolled into one.
Cons:The markup tool doesn't have shapes, only a pencil.