The context help (F1) seems only to work, if the correct #include statement is in the code. I tried "cppref.qch" and also the Linux Man Pages (available here http://developer.qt.nokia.com/wiki/Qt_Creator_Documentation_Gallery) with Qt Creator 2.2.1 and also the latest nightly build of 2.3.
Normally, a context help system should be independent of the syntax parser, i.e. the include files, as it happens often that one would like to know the correct include file for a specific function.
See also here: http://developer.qt.nokia.com/forums/viewreply/53388/