I am not a Wunderlist expert, but in my opinion Microsoft handled this surprisingly well. Whereas it used to be that big software companies would buy up challengers and more or less shut them down in order to protect their own mediocre solutions, this has not happened with Wunderlist. When they announced To Do they committed to keeping Wunderlist going until To Do is as good as Wunderlist (and yes, this is probably where the debate can start now). The Wunderlist team (minus Christian Reber) turned into the To Do team. I think it is understandable, that MS tries to concentrate their resource and efforts on one product at some point. For many founders like Reber it's probably not nice to sell out and then see changes happening that they do not approve of. But here - to me - it seems less justified than in many other cases (ie. those who sell to Facebook...).