Redhat comes with vim and xemacs (and others), which are not really that new *g* and likely the most commonly used editors (when not working on bigger projects), so I don't really agree that contestants are put under experiments.
These editors have all features that I can imagine being useful in such a contest (syntax highlighting, automatic language-dependant indentation, substitution using regexps, advanced navigation, ...).
The reason for not having IDEs like Kylix C++, Visual Studio etc. might be (just a guess) that those come with their own compilers, which, in some cases, behave different then GCC. This means an additional effort for the judging and system staff. I'm not sure, but I think in last year's finals, you had to choose whether your submission should be judged using GCC or the compiler coming with Kylix.
http://www.eclipse.org/ has documentation (though i haven't looked at it).