Yes, most definitely I used the sour cream. I even bought full fat sour cream for the first time in years. Given that the soup itself is so healthy, I figured a bit of extra fat from the real sour cream wouldn't break that.
I had it for dinner again last night, and the recipes are right... it's much better the next day. I have some for lunch today; I'll be interested in seeing if it's even better still.
The next time I make it I think I'm going to go more traditional and make a beef stock.