The Joomla 2.5 documentation is still very sketchy - for a LTS only 3 months in!! I think as a matter of urgency we need to finish some pages e.g. Complete documentation on Standard form field types etc.
The Cookie Page really needs a complete overhaul - most of the stuff in it backdates to 1.5. The documentation team's projects include a Joomla 1.5 template tutorial. This is pointless (and also hasn't had a update since Jan 2011)!! This needs to be pushed along.