No pre-installed software
I'm a Java-Documentum developer, so I need to start at least one VM besides Eclipse (sometimes NetBeans).
As a developer, I don't need anything else than the OS (of course, all the hadrware must be functional). If a need a software, I can download and build it. I mean: no PHP nor Ruby-support (etc.) pre-installed. Furthermore, I believe the system must be clean & clear: just the basis, so it can grow up according my needs.