Disclosure: I am a heavy Apple fanboy, I love the devices, apps and services especially for how seamless they work together (and at all).
iCloud, not the proudest chapter in the Apple's book of products. Cumbersome in the beginning, lots of service problems, bad user experience all over the place. For a long time Apple struggled to get iCloud to a decent quality level. It seemed the rigorous standards that Apple always held high for the design and quality of their hardware and software were not applied to the internet services of the company.
Today my feeling is that the quality of iCloud is on par with it's competition but it still is the weakest part of the Apple offerings. Apple as always has done a great job in integrating iCloud seamlessly into all the products they offer and the user experience within the Apple world is finally as good as you would expect it. But this wonderful user experience collapses if you try to access iCloud services and data from outside of the Apple universe.
Starting with that you can only run a fraction of the iCloud services on devices not coming with an Apple OS (namely Android and Windows) e.g. try to use the share photo feature of the photo app with someone who does not use an apple device. But that is just the tip of the iceberg. The fundamental problem of iCloud is that it is not designed to be open for hyperintegration. As you can read here, the possibilities for third parties to integrate into iCloud are really restricted compared to Google or Microsoft.
It seems that this is intentionally. Apple wants to keep it's universe intact. "You can only get all the advantages of our user experience if you stick to our products." And this way of thinking is one of the pillars of Apple's success: by having tight control over all the bits and pieces (hardware, software, services) that combined make up for a great user experience Apple outperforms it's competition in users satisfaction by far.
But what will be the effect of this kind of thinking in a hyperintegrated world? So far Apple regularly has build anything a user needs themselves. There is apps for personal communication, office apps, apps for music, video, photos, even AppleTV. A cosy world where everything works well and together. In the consumer world this suite of apps and services is so complete that the typical user does not need anything more than what Apple offers. In the business world it is fair to say that at least a part of the users use some of the Apple apps like contacts, calendar, mail, messaging (in that order) but although I don't have exact numbers I think this is maximum half of the business user base. The other "half" uses Microsoft and especially Google services instead. If we talk about the office apps that Apple offers it is even worse, I would guess max. 10% of business users actually use them.
So Apple's position in the business space is not the best already. But what will happen when hyperintegrated apps will get more and more successful? Apple does offer a vast and extensive array of APIs for developers, but these can only be used if you run your app on an Apple device. If you develop a service that is running in the cloud (SaaS) or an app that is supposed to also run on non-Apple devices you can not use these APIs. Because of the restricted way to access iCloud data and services as a third party it is very likely that most of the future hyperintegrated apps and services will concentrate on hyperintegrating with the Google and Microsoft eco-systems. Developers need good tools, and Apple is not offering them one. So if you want to take advantage of hyperintegrated apps, using Apple apps and iCloud will not be a option any more.
In a hyperintegrated world I see only two strategic options for Apple:
a) Apple will not play any relevant role in the business space. The apps, services used by business users will run on Apple devices, but they will not be from Apple. Apple's apps and services will only stay relevant for consumers
b) Apple is (hopefully already) developing a full blown modern API for developers (like the cool Microsoft API) and will invite developers to integrate seamlessly into iCloud and the Apple apps. Depending on when this API will be revealed Apple will keep a bigger or smaller chance to get more successful in the business world.
I don't dare to predict Apple's strategy here. I certainly would recommend b), but Apple has not shown any sign that it will open up any time soon.