Since the beginning of 2010 when the iPad was released, there has been no end of debates over whether it is suitable for creating content, or whether it is primarily a "content consumption" (ugh) device (as if the choices were thus limited…

. I am resolutely of the opinion that the iPad is an easel that very much supports serious
creative endeavors given the right environment.
I unfortunately had (as you may have noticed) to qualify that last statement. Besides a few colleagues at work, two examples of iPad-using people that I base this statement on are
the Macalope and
Harry McCracken. And these examples have something in common: in all three cases, once the work is done, the documents are sent, handled, stored, etc. by either a corporate server, or a publishing CMS, or some other similar infrastructure. Here the iPad only needs to make a good job of storing the document for the time necessary to complete it; once done and sent, the document can even be removed from the device.
Let us contrast that with another situation. My father is a high school teacher; for the last 25+ years he has been working using computers, preparing teaching notes, transparent slides to project, diagrams, tests and their answers, student average note calculation documents, etc. on his Macs (and before that on an Apple ][e). He shares some of these with his colleagues (and back) and sometimes prints on school printers, so he is not working in complete isolation, but he cannot rely on a supporting infrastructure and has to ensure and organize storage of these teaching material documents himself. He will often need to update these when it's time to teach the same subject one year later, because the test needs to be changed so that it's not the exact same as last year, because the curriculum is changing this year, because the actual class experience of using them the previous year led him to think of improvements to make the explanation clearer, because this year he's teaching a class with a different option so they have less hours of his course (but the same curriculum…

, etc. Can you imagine him using solely an iPad, or even solely an imaginary iOS 5 notebook, to do so? I can't. Let us enumerate the reasons:
- Sure, one can manage documents in, say, Pages. But can one manage hundreds of them? Even with search this is at best a chore, and it's easy to feel lost as there is no spatial organization; and search could return irrelevant results and/or not find the intended document because of e.g. synonyms.
- If one remembers a document, but not the app which was used to create it, it's hard to find it again, as the system-wide search in iOS cannot search in third-party apps (at least it couldn't when this feature was released in iPhone OS 3.0, and I am not aware of this having changed), so one has to search each and every app where this document could have been made.
- In some cases, for a project for instance, it is necessary to group documents created by different apps: sometimes there is no single app that can manage all the different media for a single project. On iOS these documents can only exist segregated into their own apps with no way to logically group them.
- If there is a screwup, as far as I am aware it is not possible to restore a single document from backup, in fact it does not seem possible to restore a single app from backup, only full device restores, which may not be practical as it likely means losing work done elsewhere.