How I Use It
I haven't used this app over hangout yet, but I would like to in the future. We have used it on iPads as a helpful tool for individual students to work and draw on in math. It is not all that different than using white boards, but it's nice because they can save their work and refer back to it later, something you cannot do, of course, with white boards. The only problem with this app is that students are tempted to doodle with it because it's very fun. Doodling could be an end-of-class incentive.
This app would be okay as a teaching tool. Not awesome, not horrible. It is fun in that it can be run over a Google Hangout, so several students can see what is going on at once. If students wanted to do an after school study session, this would be great to supplement explanations of concepts, as students can write equations, draw graphs, etc. It also may be beneficial in large classes as students can look at individual screens and see what the teacher is doing, then students can provide examples at their own computers that the whole class can see. It could serve teaching better if some of the stamps were specific to certain content-areas. For example, division and multiplication symbols, more shapes, etc. If students are using this app not on hangout, but rather on iPads, they could hold up individual iPads to provide answers to specific questions (like white boards).