Fixed width or full width websites?

I recently read an article on A List Apart called Fluid Grids. This got me thinking on how many websites use fixed width columns and how many used full window width to display content. Certainly when the web was young, the design of many websites (quite often personal web pages) were full width, expecially with the typical resolutions being 640×480 or 800×600 if you were lucky. The lack of screen space meant that to have any area dedicated to ‘airy’ white space would result in lines of text comprising three words. Since then, we’ve had more screen space to play with and then the dilemma of to fix or not to fix lurks around every corner.