Thank you for your review! It's great to have you testing the new Busy :)
About the editor your post is not lost when you close the page, it's saved automatically in your drafts, you can manage multiple post drafts and they are synchronised across devices, you have the same drafts if you login in your desktop or mobile. There is an indicator when the draft is saved near the button "Publish", but we probably need to make these more visible.
I'm also waiting for communities :D, i'm sure it will help a lot content discovery and it's something we want to integrate when possible.
Now we mostly been working on the user experience for the same use case than Steemit. We definitely need something different and your idea of posting directly from the feed, it's part of the things we want to do and the way we tend to go.
I will make sure your comment is top so that people know there is a draft function. (it's a really good idea)
I'm really glad to know that you are looking to differentiate from steemit.com. You've been doing an amazing job and I can't wait to see what you'll come up with in the future.