How I Use It
We had one Google hangout session with students with mild success and multiple Google hangout sessions with teachers. I have to say that it is much better for teachers to use for PD because of the fact that it is appropriate for expanding PLNs (Personal Learning Networks) and allows teacher to access each other at any time of the day as long as they have Google accounts and webcams. We did a group project for students across classrooms in a school and it worked fine but it wasn't that much different than Skype. We also had to set-up multiple Google accounts for students which took time. Overall, it is a great free tool to use for webcam collaboration and is an almost instant online webcam experience (or planned experience) when you want it. There are also great Google Hangout PD sessions you can join.
My Take
Google Hangouts is a wonderful free tool to allow collaboration and discussion among students after-school, between classrooms, between schools, etc. It also allows free online PD opportunities for teachers as well. Overall, you can't beat free but it does require everybody to be on Google+ and have webcams. There may be issues with technology and privacy especially if it's not used in a closed school environment. It can cause technology overload if your school or district does not use Google for Gmail, Google Drive, and other Google apps since all Hangout users have to have Google accounts. And there isn't much of a difference between using this and Skype unless, as I said, your district or school uses Google for other things so having a Google account is either required or recommended.