I am not using Busy still. But what I believe is that it will become the standard way of interacting with the Steem blockchain.
As far as I know, Ned and Dan created Steem and after that Steemit in order to allow people to actually interact with the Steem network. But Steemit is just a way of interacting with it. Created because there must be a way to do anything with Steem.
It works, but it is not optimal.
Busy, again, as far as I know, is a solution crafted for the interaction with Steem. They only have to upset about that and leave all the other to Dan and Ned.
Yes, they needed an example of an application running on top of the steem blockchain. That is exactly why steemit was created.
I believe BUSY will become ONE of the defacto standards. Yet if this keeps going there could be a lot of different types of things. Hopefully all interconnected somehow.