My Take
I think this can be a great teaching tool. The site is fairly easily to use. You can create an account to go back and edit your links. If you do not create an account and you lose your link you will not be able to get it back. I really like this website as a quick tool to have instant feedback or brainstorming type responses. I recommend using this if you need a quick response out of students or a quick talking point with students comments.
How I Use It
I have used Answer Garden to have a quick brainstorm on a topic. For Instance I asked my students to write any words they can think of when they hear climate. We created a large word cloud with all of their tweets. Recently, I had the students break into groups to create their own word clouds on what types of weather relates to the clothing on their card. Answer Garden is in real time. The students responses will be seen immediately. The students like the idea that they are tweeting a quick response and that they can see it in real time.