Apple has a very bad reputation when it comes to taking over products like this. TestFlight is the prime example. TestFlight basically disappeared for a year until coming back as a more limited and slower Apple branded service. And by slow I mostly mean, it takes 6 months for bugs to be fixed or for exciting things to happen. Agility and innovation of a startup basically ends when Apple assimilates a service.
From the blog posting it is also not very clear what will happen to existing iOS customers. Can I upgrade my plan? Can I expect service? Will the existing infrastructure be maintained?
I'm excited about what this could mean in terms of Xcode and Xcode Server improvements. Or maybe even a hosted CI service at Apple. But that it all long term 'maybe'.