I've never actually used TypeScript until today, but just the tutorial code takes forever to compile, this snippet took 2 seconds for example, whaaat??

    interface Person {
        firstname: string;
        lastname: string;
    }

    function greeter(person: Person) {
        return 'Hello, ' + person.firstname + ' ' + person.lastname;
    }

    var user = {firstname: 'John', lastname: 'Doe'}

    document.body.innerHTML = greeter(user);

It's a shame really, because it looks like a really cool project.