Depends on your audience. Those % are right for geeks.
I run many sites. If I choose one that is very "Joe Public", such as one of my mortgage information sites, then I see the % of 800x600 is 9%.
Don't forget, screen resolution is one thing, but it's the wrong value to look at when designing your pages. You need to look at browser window resolution. The size that most consumers have their browsers open to. Most don't have them open maximized. If you look at browser resolution, then roughly 800 pixels wide is VERY common.