I have tried steempeak and can say that this interface is simular to steemit but have some improvements. 

Here are some nice features: 

- Votesilder

- Notification 

- Activities tab 

- Bookmarks 

- Templates 

- Scheduled Post 

and many many more. 

How it's work? 

It is like steemit a interface to interact with the Steemblockchain. Every action you submit to steemit or steempeak are saved on the steem blockchain. 

But is it worth to replace it with steemit? 

I can recommend to steempeak. But you can also use steemit or both. Nobody limits you to use just one of these interfaces.