I'm using Edmodo with my class this year. It's been a great resource and over time they have added new features to it that have made it easier for teachers and students to use. I really like the polling option that allows you to poll or quiz the class with the click of a button. THe students are very engaged and always excited to use Edmodo since they get to interact with other students in the class. I thought a challenge would be reminding my 4th graders to stick to chatting about educational topics but that has been fairly easy for them. A challenge has been keeping it updated on behalf of me, the teacher. I usually upload a bunch of resources at the beginning of each unit but it's been harder to keep it going and log in each day to keep it current.
I like how the article "Building an Online Learning Community" mentioned the teacher presence, student presence and cognitive presence being important aspects of the learning community. I also really liked the table about community evolution and how the students roles and instructor roles change over the phases of the course. This is important to note and be aware of as I continue to use Edmodo next year with my class.