It's certainly not my preference in any breed, but I own a dock-tailed dog. It was actually a bit of an accident; she was so freaked out about the world when I brought her home, I didn't even realize she only had a nubbin. It was pinned down so tight, I figured there was more tail that I just wasn't seeing.
There is no end to the expressions her tail can show. Obviously it probably harder with dogs who are docked very short like Pembrokes, but Meg's is probably 2 - 3 inches long. It can be straight up ("EXCUSE me, but what do you think you are doing at my barn, strange dog?"), straight out ("I'm pointing; so what if I'm not a pointer?"), tucked tight ("My world is ending; the terror is taking over"), going in perfect circles ("You are my most favorite person in the world right now, and I'm beside myself that you are in my presence"), slow, careful wags ("You are holding some food that I would really like to try, so I'm being very polite), insanely fast wags ("OMIGOD THAT FOOD IS COMING TOWARDS ME"), and everything else imaginable.