There ARE keyboards available that can be used with the iPad. There are several bluetooth keyboards available, even Apple makes one. Most of the others that I have seen are combined with covers. There is nothing wrong with the virtual keyboard either. To say that the iPad is highly limited as a productivity tool is outright stupidity on your part. I use it just fine without a Keyboard and use it with Numbers, Pages, Bento, Keynote, Day One, OmniFocus, Facebook to name just a few of the productivity apps.
As for the file system, I think the whole idea behind the cloud is NOT to have the files stored on your device taking up precious space. This way the iPad memory can be used for other things such as apps. It also means that with the documents in the cloud the latest version of of each document can be accessed from the iPad, Mac, PC, or iPhone since they area all stored in the same place.
Yes, you can use the ipad for many things, but part of my definition of productivity is if it's the fastest/most efficient use case. Sort of like you could walk to Mexico from NYC, but it's not going to be very productive to do so.
I know that you can attach a bluetooth keyboard, but add the keyboard and smartcover to an ipad's weight and you are fast approaching the macbook air 11's weight. And again, it's unwieldy to carry the entire contraption around with you. Only argument might be battery life, but that's offset by raw computing power.
I bet that if you used a spreadsheet on a macbook air vs an ipad, you'll be much faster on the macbook air. Or a word processor, etc.
I've got nothing against the ipad. I have one. But it's never been a productive platform for me when I need to get work done, which involves spreadsheets, word processing, photo editing, and general keyboard-related input. Maybe I'm a really fast typer or something, but I doubt it. Over time I end up using what works the most efficiently and for many cases, the ipad is not it.
It's not an issue of familiarity. Laptops aren't going away anytime soon.
And the cloud doesn't work when you're offline, but that's not a big deal these days. What is a big deal is the fact that data is getting more expensive and it's not unlimited, so I would not want to sync media etc in the cloud.
I still remain unchanged about the file system being a relic. It is odd when I want to open a word document. And I have to go to goodreader, or a word processor, or mail first... and remember which app I saved the document in. And then open the document. The mental model is such that your task is that you filed the document somewhere in a central place (your folder) and you choose an app to open it. With the Apple approach, I could well open goodreader, fail, open pages, fail, then remember I stored it in mail, and then open the document. It's odd.