You don't need a VM to compile something into Javascript but the VM buys you a fast edit/reload cycle and some tooling like a debugger. Also Dart can be used as server-side language and there the VM makes sense. It can also be used as an interpreted language just like Python and here it doesn't hurt if it's fast.
Even if _you_ don't put type annotations in your code, the IDE infers types (locally) and gives you useful warnings and code completion.
Less than 1/3 through I decided to started to zone out. I don't understand why you need a VM to compile something into Javascript. Also the optional typed language feature is just odd (okay I can see working in groups and wanting to empirically let other developers what type a variable is), but it's just not something I see myself wanting to learn to do what I already know.
I was also interested in the Angular talk, which was good, but it left me thinking Angular is to CakePHP in the MV* javascript world with all the built-in automagic.
Overall some pretty good talks at this.