Great if you put the work in
If you put the time in and create "workflows" for your group this can be a very useful website. An example would be setting up a bank of websites for students to do research at and then reporting back to you through edmodo on what they learned. You need to vet and create the resource lists and think up the projects, but as a management tool, edmodo works great. It is also great for putting up class quizzes and checks for understanding, quick and seamless. It would be nice if the service had some things I find useful in Google Docs, like reading over students writing and giving them comments and marking their writing, so they can see how they did specifically. The service does require A LOT of norm setting and discussions with students on how to properly use it and it will take a lot to get it up and running, but it is worth it once you have it going.
How I Use It
I use it in much the way I describe above, I create a project for students then share the websites through edmodo. I also use google docs so kids create slideshows and documents there then share them with other kids and I on edmodo. Also I use it for quick quizzes and short response questions on what we are learning in class (always easier to organize this than a bunch of papers). Students enjoy the wall on edmodo and writing back and forth to each other. Also the kids loved sending me messages and talking to me through edmodo. This did not work for lower kids who were not independent or couldn't hold themselves accountable, you need to really be hands on with them and helping them navigate the site and resources you put up. Higher level students loved edmodo and really had opportunities to push themselves and explore things they were passionate about.