I'm currently using Collaborize Classroom to teach a class. It's not so much a classroom management system (like Edmodo) but more of an online discussion forum for your students to post, comment, and reflect on questions and assignments. It's a nice-looking site, but I think a standard discussion forum might serve the same purpose and work a bit better. That being said, CC is an easy way for students who are new to discussion posts and comments to get comfortable with this type of system (and it's free!).
I used Collaborize Classroom with my 9/10 English students. I agree with Randall that it is not a typical classroom management system in that it is not trying to do a million things. The good news is that it is simple and intuitive because it does not offer a ton of features that I don't need.
I do not think that it is comparable to a standard discussion forum because the discussion component is so highly developed. There are four different question types- Yes/No, Multiple Choice, Vote or Suggest and Forum- that allow you to structure discussions to add variety to the conversations that you have with students. As a teacher it is fun to mix it up. Other LMSs offer threaded discussions, but my students found that boring after a while.
The Categories allow you to group your students in any way that works for you which is awesome for group work. There is a Results Page that allows you to publish any discussion topic to create a colorful pie chart showing how many students voted Yes or No on a topic or how many students selected a multiple choice option. It makes it really easy to bring the outcomes of a conversations back into the classroom for follow up discussions, debates, assignments, etc. The Participation Reports have made it simple for me to keep track of participation for grading purposes while also keeping all work saved like an online portfolio.
Your descriptions make it sound like a useful and easy tool to use for collaborative work and discussions.