In my opinion, if a company has the resources to generated additional content to a game between the time it's sent off for disk manufacturing, there should be zero known unpatched bugs at launch. If you can pay people to model and texture horse armor, you can pay people to debug your code. On principle, I won't buy DLC for a game if I encounter a significant amount of bugs. That just tells the developer that it's ok to be lazy in their debugging process, because we as the consumer will continue to throw continually increasing amounts of money at them.