Just a users perspective - I am an architectural photographer and as such use the STC almost exclusively with vertical (rise/fall) shifts.
This places the handgrip on the bottom when shooting. It sounds awkward, but I have not had problems holding the camera in the field.There are small ridges on the left and right front of the body (when in the vertical position) that make it feel quite secure in the hand.
Mostly, it is sitting on a tripod anyway, so its completely a non issue.
One thing that I have found very handy is having the electronic level on the IQ180 back. I'm finding this, combined with the bubble levels on the Alpa very useful.
I have had discussions with the team at Alpa about introducing a handgrip that suits those of us who prefer vertical shift as our default movement. They took the feedback on board and I'm sure will give it due consideration.
The fact that the viewfinder fits on all sides of the body is very handy if you use it a lot. You can fit it wherever it suits, though I did find the screws a little tricky to fiddle with with gloves on when it is cold (I was shooting in Snow at xmas in Switzerland). The camera still feels secure in the hand in the summer heat, even with sweaty hands (its currently in the mid 40degC range in Dubai and will be up into the 50s in a few weeks). I certainly appreciate its light weight!
In the end, it's all about the pictures.