Does the smart cover keyboard on the iPad Pro have any features that a bluetooth keyboard wouldn't? If you buy either model of the iPad Pro, you have the option of using the smart-cover keyboard. 

Aside from the fact that the smart keyboard draws its power from the iPad Pro (using special contacts for that purpose), are there any other additional features that couldn't be done using one of the many bluetooth keyboards designed for tablets? 

I don't see any special keys on the smartcover keyboard, which leads me to believe the answer to this question is a simple: No.
Well the keyboard does act as a stand, you get a folding triangle bit at the back and it holds the iPad at 45 degrees, so you can stick it on your desk and type away. The bit in contact with the desk is like felt, so the whole thing doesn't slide around. There is also a magnetic grip/strip that keeps the keyboard secure when its in the stand, so again it doesn't slide around. It all feels very secure and connected.

The keyboard also opens out completely and folds over the iPad and acts as cover for when you're carrying it around, so the screen is protected from scratches and other knocks. In this mode the keyboard has a small magnetic contact that switches the iPad off when you close the cover and wakes the iPad up when you open it back up.

Also the keyboard draws power only when you hit the keys, so doesn't put a drain on the battery quite like running bluetooth does.

Its also smart enough (because of the connector) to understand that pressing CMD + TAB together means switch between apps like you get on a desktop

So the keyboard really acts as a keyboard, stand, anti-slip device, scratch protection, screen cover, better battery, CMD+TAB  and 'go to sleep/wake' combination device.