Most dialogs have a help button that takes you to the relevant online documentation
You can use Ctrl-[ or Ctrl-] to indent/outdent a block of code in Coder view
Both in the Coder and Builder views have a demos menu with plenty of demos
From Builder you can generate and customise the python script that controls your experiment (might be a good way to learn a bit of programming).
Avoid snorting Pepsi
Most buttons have tooltips if you hover over them
PsychoPy can handle many different units once you've calibrated your monitor (see documentation on general > units)
Menu items show you the current key bindings (which can be configured in preferences)
Use the source. PsychoPy comes with all its source code included. If you know python, you'd be surprised how easy it is to find your own bug-fixes. (Warning: can become addictive.)
PsychoPy is free. Please cite the relevant papers (Peirce 2007; 2009) if you use PsychoPy in published work. 
The mailing list is a great place to ask questions and receive updates, at http://groups.google.com/group/psychopy-users 
Coder: Did you try typing python commands in the Shell window yet?
If you buy a computer, make sure it doesn't have an "Intel integrated graphics card" (or make sure you can upgrade to an nVidia/ATI replacement)
Builder: right-clicking on any 'color' parameter will bring up the system's color-picker.
Coder: you can click the color-picker icon on the toolbar. The rgb color triplet will be saved to the clipboard (in PsychoPy's rgb color units, -1..+1 not 0..255), which you can then paste into a script.
In the Builder, you can right click on things to bring up a menu, e.g., to remove a trial.
To flip a Patch stimulus, give it a negative 'size', in x, y or both
Coder: most commands like stim.setOri() can also take an operation argument (e.g. '+' to increment orientation)