How do you ensure, that you can checkout the code into Eclipse or NetBeans and work there with it?
Edit: If you not checking in ide-related files, you have to reconf
For the most part I'd agree with seldaek, but I'm also inclined to say that you should at least give a file that says what the dependencies are, what Java version to use to compile, etc, and anything extra that a NetBeans/Eclipse developer might need to compile in their IDE.
We currently only use Eclipse and so we commit all the Eclipse .classpath .project files to svn which I think is the better solution because then everyone is able too reproduce errors and what-not easily instead of faffing about with IDE specifics.