Here are more thoughts on the more common threads I'm seeing in your replies.
Re: Web designs are getting wider over time, and wider is better.
I think as a general trend our older themes on WP.com are narrower and newer themes will probably be wider. This follows what raincoaster said:
None of the web designers I know are even thinking about anything less than 1024px wide monitors (although some of the netbooks out there are 800px wide).
Right now the standard is 960px wide to make sure the design works in most screen sizes. But, that includes the sidebar, any design elements (border, background, margin, padding), so the actual width you have to work with could be much smaller.
So as screen sizes get larger in general, web design across the board will adopt a wider default layout.
We're also seeing trends in web design that lean towards narrow (microblogs, lifestream blogs, link blogs) and designs that lean towards wide (magazines, news portals, showcase sites).
So when we launched a new theme, like Vostok, many of you probably thought "Ew. Too narrow!" But for each one of you that said that, I imagine another person said "Great, exactly what I wanted for my link blog. No clutter, narrow width to show off my link or photo."
Re: wide sidebars, lots of sidebars, more sidebars.
I think that's an entirely different conversation. We're discussing the main content area: where your post content is displayed.
So yes, a much wider theme width in general would allow for a usable width in the main column plus many sidebars. But, I'd like to focus the conversation on just the main content area.
Re: "I want to include bigger photos with my text."
There are tradeoffs here. Bigger images take longer to load. Speed of loading is very important—it affects the perception of your site if your content loads slowly.
As a point of reference, look at popular blogs: http://technorati.com/blogs/top100/ and take just the top 25.
Designers and art directors at these companies spend oodles of time and money creating the perfect blog layout. In looking at the top 25 blogs, almost all of them have a width somewhere within 600px.
They use photos to illustrate the posts, but they aren't huge photos.
Re: "I don't want wasted space on the sides."
Just because a design has empty space doesn't mean that space is wasted. It's often left empty on purpose to give breathing room to the content; its purpose is to frame the content so that it's both pleasing to look at and easy to read.
Also realize that not everyone has a big monitor—many folks will read your blog on alternate devices and with small laptops. Chances are that your view of the design isn't what everyone else sees exactly.
No design is going to please everyone. Many of you say "Don't waste side space!" but then others say "...not looking cluttered, with a fair bit of white or blank space." :)
I personally wouldn't worry about your readers complaining about "dead air" on your site—that means they are probably not engaging with your content itself, which isn't a fault of the design. Again, look at the top 25 blogs with a wide monitor and you'll see that with most of them the layout does have empty space on the sides when you get above a screen size of 1280px. I'm not saying what they do will work for you, but it's probably well-researched and well-tested on their many, many users.
Re: "I don't want people to scroll too much."
Scrolling is part of how the modern web works. People are used to it. The argument that you wish to avoid scrolling on long posts doesn't make sense in today's web. Wouldn't you rather people find your writing readable and approachable? Look at a typical book on your shelf—the line lengths are intentionally designed to allow you to quickly scan and not have too much horizontal movement. There are many, many years of graphic and layout design research to back this up.
I think that is why you find so many fixed-width layouts, not only with WordPress themes but online in general. They give the designer confidence that the presentation will be managed in a useful and eye-pleasing way while maintaining usability.
Making your articles appear shorter by making them wider won't necessarily make them better and more appealing to readers. It's about the content: if it engages people, they'll read it.
Re: "I post photos and don't want text to wrap around them in a narrow line."
To me this is a simple page layout technique.
If you want a big photo in your layout, use the full width so that the photo fills the entire column nicely. Try to avoid using a photo size that is almost the full width, that will result in the look you are complaining about. For smaller images to flow with the layout, pick a small or medium size like 33% or 50% of your theme width so that text will wrap nicely.