There are three main aspects to Edmodo: Social/collaborative; virtual classroom; and applications. I find the social aspect to be slightly lacking at this point. I was pleasantly surprised to see a few of my colleagues at my school that were already Edmodo members. Communicating with colleagues is a great thing, but from what I have seen many of the members are possibly fake? People that don't write good English; or ask really strange questions? I'm purposely sounding confused because I'm not sure if I'm seeing some kind of spam or something. These are my first impressions, so maybe down the road things will get better here. It would be a good tool to collaborate if the right people were on there. Twitter it ain't.
Finally, purchasing apps is a mixed bag for me so far. Some of the apps that are available look to be useful in this climate; some maybe not so much. Some are free, which is cool; but some are really expensive. I went ahead and used my credit card to buy some store credits. After I had purchased a couple of apps I discovered I had actually only purchased a one-year subscription. The store was less than up front about that. Oops. That's dirty pool. It's like the Amazon store: great potential, but too much 'nickel and diming.'
I really do love the potential of Edmodo. I would love to learn more about it. So I will keep exploring and discovering if the reality lives up to that potential. A mixed bag so far, but very intriguing.