This is great!
I'll be interested to see how Steemit and Busy adapt to these new specialized front ends. They'll need to enable some filtering just like Steepshot is planning, but in reverse. The current "new" and "trending" pages won't really hold up well if flooded by blockchain content from sites that have formats akin to instagram, twitter, and youtube.
The sites will need to adapt to either present everything in an appealing way, or focus on written longer form content.
These concerns aside, I'm totally in favor of all of these sharing the same Steem blockchain.