Yeah I decided to go with a layout optimized for a min of 1024x768 res. The content area is 1000 pixels wide.

We have been online for over 4 years and get about 7,000 unique visitors per day. Out of all of the visitors about 11% use 800x600. The rest are 1024x768 and higher (
stats).
It really is a great system. Even with our hacked threads with high queries (about 16 queries on showthread) at about 200 visitors the server load sits around 0.80 to 1.30 on average. This is on a single dual Xeon server.
I am always looking for new ways to optimize the site/server/vb as well as ways to add functionality.