If you want to decide on your own point spacing, you can use the Sextante Toolbox with SAGA functionality activated (you'll need to install sagaSAGA - www.saga-gis.org/http://www.saga-gis.org/en/index.html - and specify the installation path in sextante). Use
Use the 'polygons to line'"Polygons to Lines" geoalgoritm followed by the 'line to points'"Lines to Points" one. You can create a model in sextante that combines these into one step as well.
Note:Note: you have to make sure you install the right version of SAGA - I think its 2.0.8