Yes, use the official SDK. The problem with the "Open Tool Chain" is that there's no guarantee of backward compatibility and hence you'll always be at risk that Apple breaks your application. If I was doing an app. for business reasons I'd go with the official SDK.
Sure, you appear to have lost a few things (perhaps the most significant is that ability to run in the background). I suspect that the biggest benefit of the Open Tool Chain is that it will provide a way for Apple to see what people want in the real SDK and they can cherry pick official additions as necessary. The essentially did that with the entire SDK idea in the first place.