What exactly is the frustration from it? I find it perfectly fine, if not better than using a laptop for writing "simple documents".
In fact that's exactly the use case most pro writers that use an iPad use it for.
When I needed it there was also no splitscreen, which I acknowledge would make things easier. The situation might be better now, but my sour experience forced me to move completely away from Apple at the time.
Well, I don't normally use the mouse when I'm writing a document. I even prefer full screen, full focus mode in writing apps like iA Writer and Ulysses (also on the Mac).
That said, most shortcuts one would use for writing work just fine (select all, copy, paste, etc). And more from what I see here: http://www.laptopmag.com/articles/every-ipad-keyboard-shortc...