I make a mustard sauce that is my personal favorite, but I don't use it in comps.. any more.
I used to use it as a mop for my butts and I loved the flavor. But I never got anywhere above middle of the pack with it.
I took a cooking class from Chris Marks once and asked him about it. He told me that in the Mid West (which is the only area I compete in) using anything other than your basic KC-Style, sweet & thick sauce is not worth the risk.
He said that while it might be really good, it just is not the flavor that the judges expect or are looking for.
Our last comp I used our Kentucky Bourbon sauce (which is similar to a KC-Style sauce but with bourbon in it) and took a 7th place walk. Same rub, same cooking process, just a different sauce.