As one who has owned keyboards for every iPad since the iPad 1 and Apple's keyboard dock (anyone remember THAT?!) perhaps I can explain...What I don´t understand is why everybody made such a fuss out of using the iPPs as a desktop replacement because of the Smart Keyboard. Keyboards for iPads are around for many years (e.g. from Logitech). For me the screen size of the 12.9" iPP is the real difference regarding using it for working stuff. I am using the Smart Cover to keep it light and thin and taking a Apple Magic Keyboard in the bag if it comes to heavy typing (same width than iPP 12.9"). This keyboard works without compromises...
Yes, it is true that the 12.9 screen is a big factor. But never before has there been a keyboard cover that is as thin and light as the Apple Smart Keyboard (ASK). Except for the slight bump caused by the keyboard, it is as thin as the non-keyboard Smart Cover. THAT is significant.
The fact that it is powered and activated automatically by the Pro itself are more pluses. It is only relatively recently that non-Pro keyboards included this "auto-on" capability. The Belkin Qode Ultrathin keyboard case for my Air 2 did that... VERY convenient.
The ASK is far more portable than Apple's Magic keyboard or Apple's older Bluetooth keyboard. I can pick up the iPP + ASK (as a single unit) and walk to a meeting. With the Magic or BT keyboard, I'm toting 2 separate, individual items... which would require me to use a case/tote to transport easily. Separate charging/battery changes for those separate keyboards are additional compromises.
Because the ASK is a cover and not a case, it is easy enough to quickly detach and use in "tablet" mode.
After spending a week with my 12.9 Pro and ASK, I think that I'm settling on both the ASK and Smart Cover... because like Almond Joy and Mounds, sometimes you feel like a nut, sometimes you don't.