For me this was one of the top bonuses of the BMD cards.
It was not the core feature I was looking for, but when I found out about it, I used it very often. I do not have endless room at my table and using the video monitor as extended desktop was a perfect solution for me.
I think that more users actually used the extended desktop on a regular basis than color. And if you are a color user you are already (hopefully) proficient enough to turn your extended desktop off.
The needs of all users are quite different I guess, so it would fit better if the choice was still there.
Please provide a fix for that.
Thanks!