The $10 plan looks not too bad, for me anyway. It looks like they modified their previous social plan to include the 50mb of data.
Previously they only had a $10 social plan for Blackberry that gave access to BBM, IM, few social sites. This one hasn't changed, but it would have been nice for it to gain 50MB of data as well.
The $10/50MB is a new plan for non-blackberry users.