How many times have you started a build and found that you forgot your “using“ references?  Then you had to remember which references you needed for the particular class you were implementing?

Now there's basically a smart tag in the IDE on the class reference.  Open the tag, and you can click on an option to add the “using“ references for you.  Since we have so much metadata stored in assemblies, it's just a matter of reflection to figure out which to use.  Such a simple concept, but boy does it save time.