i was one of the 800x600 holdouts, but that's over for us. we only design in 1024 now, and our sales went up across the board with that change.

most of our surfers are at 1024. also we now have more surfers at 1280 than 800, and a site designed for 800 looks really REALLY tiny in 1280, so i'd say it's a good idea to check your server stats or google analytics to see what resolutions most of your surfers are using.