Another minor detail that bit me for a few minutes today. I'm posting this so I'll see it and remember, and possibly lodge it in other people's consciousness.
Using Visual Studio 2005, adding an existing .cs file to a C# project will cause a copy of that file to be created in the project directory. If I want to link to the original file, I need to explicitly choose Add As Link from the dropdown on the Add button.
C++ projects, however, have the opposite behavior. Adding an existing item in a different folder will add a link to the original file in the original location. To create a copy, manually copy it to the project dir.
That is all.