The answer, as with so many other questions in the coding world, is that it depends. However, for the average developer CLS compliance is not a concern. For the specialized component or tool developer CLS compliance might be your bread and butter winner. For the average developer, CLS compliance is nothing more than bragging rights or an enforced rule at your organization. You probably only operate in one language provided graciously from MSFT and have little concern if your libraries will play nicely...