The only concern I have right now is that if the proposals for ECMAScript 6 change, how will TypeScript handle those changes. Things like CoffeeScript don't have to worry about that because they set there own standards. I would hope that if TypeScript ever had to make changes that was not backwards compatible, they would have some sort of tool that would help in converting the old code into the new code.
The only other thing that is Microsoft only right now as far as I can tell is that I don't know of any other IDE that supports TypeScript besides Visual Studio which is really the biggest thing TypeScript brings to the table. My hope is that other IDEs (hopefully JetBrain's IDEs will be fast on this) will quickly add support for this language.
I find it a bit ironic that the Chrome browser is used instead of IE.