Black update for 520 will be available by the end of this month or at the start of February, Usually Lumia 520 will be the last model in the windows phone lineup to get the update .. Like what happened when Amber was released.
the update is about 200 mb in size and takes more than 800mb during installation..
the task manager for closing apps is nice and there is slight perfomance improvement for my handset..
here is the screenshot of the taskmanager..