Honestly, I tried to work with Dart. I hit a few stumbling blocks during the tutorials. One difficulty was javascript interop. I also remember the drag and drop tutorials not working when I downloaded the code from github. It is really good that you covered those topics. Javascript interop in particular was a good choice. I can imagine a lot of developers may want to dip their feet in without migrating an entire project into Dart.
I think the post was a good writeup. I think that there is a void in Dart tutorials in general. It is incredibly easy to set up a standard Dart project. The idea of Futures are incredibly easy to follow. The code itself is very direct and easy to follow. The part that I always end up turning back on is when I try to integrate a real life project with Dart. I looked up the Angular port and found an incomplete tutorial. It gives me the feeling that others have not navigated that road before me, which in turn makes me wary to continue.
Perhaps a few blog posts that go heavy into the business logic of whatever app you decide to make would be more comforting. As a person who is on the fence, it would give me great comfort to see all the nuances of common CRUD apps blogged about. If you look at tutorials for Angular in javascript and are able to match those in Dart, I'll switch over.