[1] http://support.logitech.com/en_ca/product/keys-to-go-ipad
The other thing with these keyboards is that when the tablet is held in table mode, you have your fingers on the keys, which is a pain.
I tend to agree with the post above. Good for reading, not the right tool for editing.
This is the same as, say, people who prefer to use laptops docked to a large screen with an external keyboard and mouse. Most of the time, they can get away without needing all that, which is why they have a laptop instead of a desktop PC plugged into the same peripherals. But sometimes, for an especially heavy-duty task, it's good to be able to temporarily assume the next form-factor up.
Works well for me (fiction writer), but might not work for people whose workflows involve constant distraction.
(There are USB docks but they cannot really compete with real docks as they are available for PC notebooks. And Apple does not sell an external Retina screen either.)
If you prefer something exactly like a dock where no cables are involved being plugged in manually, there are several solutions available. Henge Docks, Landing Zone, and BookEndz are some examples.