If it's just making a content column wider then it's not really that useful in most cases, but if it's adding another column with useful information for the user, then it is a big deal - it makes the website that much easier to use.
to give you an idea of what kind of value can be added
Sure adding another column could be useful but as you can see by the authors tone he is talking about flow and divisions of columns and how those go well together and in all reality it sure doesn't make a hell of a difference even if you shrink something to add an extra column. After a while you get cluttered and usability/simplicity goes out the window.
1920x1200 = two windows of 960px
2560x1600 = three windows of ~850px
the other problem with this and fluid designs on wide screens is that it becomes difficult to read text when it is that wide.
the best idea that i have seen is a site (or maybe it was sites, i know I've seen at least one), where the content is 960px but then if your browser window is wider, javascript adds additional content to the right of the content, columns that come down with additional links and further navigation options.
I do this for two reasons. One is that the remaining space on my screen is for other stuff. The other is that a lot of websites ignore the traditional typographic rules for line length, and even when those rules are followed, the principle of constraining the horizontal size (including things like navigation and sidebars) in order to reduce the necessary eye movement still applies.
A fixed width page that has been well designed for 1024x768 (such as this article) is frustrating to read on my 1600x1200 LCD, and would be even worse on a 1900x1200 LCD.
Maybe an extension to CSS that permits specifying "Widescreen" or "Netbook" as alternatives to "screen" and "print" or whatever would be helpful. I'd sure like an option that says "I'm not blind and I'd like to use the pixels I've paid for."
Maybe since Javascript is ok again designers could design two or three widths and have browser page detection select the smartest layout. Having a 1024x{600,768} design for netbooks and grandma would and a 1400+ column design for people using large screens and professional grade notebooks.
I guess we have to keep waiting for http://www.w3.org/TR/css3-mediaqueries/#media1 support.
In fact, I wonder why this isn't a common option in browsers.
What if your text editor didn't let you resize the window because it thought 80 characters was wide enough for anyone (80 characters at 10pt Courier, of course)? I would be pretty mad. Users should be in control of these sort of things.
To accomodate people with bigger windows, link to bigger images so that they scale as beautifully as text.
