Nothing kills progress than having to create documentation that will never be read or updated.
Don't get me wrong - certain types of documentation are important (overall systems design, data models, for example). But unless you're going to continue to use the documentation after the project has been completed, don't bother creating it.
What most people seem to forget is that if you don't plan on maintaining all the documentation you create, you're wasting your time. Once a document is out of date, it no longer serves it's purpose. I'll expand on an adage: Outdated and incorrect documentation is worse than no documentation at all.