I wouldn't say that the majority of internet users use it - I looked in my Urchin logs and for the month of August I had an average of 12.1% use 800x600 and if you look at http://www.w3schools.com/browsers/browsers_stats.asp which had the most comprehensive stats I could find, in June 2005; 25% used 800x600 and 55% 1024x800 and the rest basically higher and looking at their historical data, that 800x600 % is going down sharply.

--Tone