I like the new trend in 1.3 of using the wp-header, wp-footer, and wp-sidebar files to make customizing and upgrading WordPress easier. I like the trick of using, for example, header.php instead of wp-header.php if it's available, which makes upgrading almost seamless. But if that's going to be the standard for customizable PHP files, then why not take it one step further. I would like to see the same logic applied to wp-layout.css, so that I don't have to go through the task of replacing the stylesheet every time I upgrade. This would only take a simple statement in wp-header.php if I'm correct. For those of us who are upgrading to the latest nightlies regularly, this would be a significant improvement. Plus, consistent logic is always a good idea.