Sorry for the major bump, but I'd rather not create a new topic for this.
I prefer fixed width over fluid. They just appeal to me a lot more. You know exactly how it will look on other monitors, as the text and content won't be spread out across a screen with a large resolution.
What the designer sees is what the user sees.Though I really dislike when the width is
too thin, to the point where the whole site sits in the middle of my browser.
There needs to be a nice balance, somewhere between 760-960 pixels wide. The only problem with these, is that if you have users with small monitors, they're pretty much screwed and will have to scroll vertically (which will ruin the experience for a user and they will most likely leave). Then again, how many people still have monitors that small? Even large corporations such as Apple and Microsoft have started (in '08) developing for users with 1024 resolution, and dropped anything smaller.
There is also research indicating that long lines of text are more difficult to read:
The ideal line length for text layout is based on the physiology of the human eye... At normal reading distance the arc of the visual field is only a few inches - about the width of a well-designed column of text, or about 12 words per line. Research shows that reading slows and retention rates fall as line length begins to exceed the ideal width, because the reader then needs to use the muscles of the eye and neck to track from the end of one line to the beginning of the next line. If the eye must traverse great distances on the page, the reader is easily lost and must hunt for the beginning of the next line. Quantitative studies show that moderate line lengths significantly increase the legibility of text.
Web Style Guide - Basic Design Principles for Creating Website
Patrick J. Lynch and Sarah Horton
2nd edition, page 97.
The third alternative would be to use Elastic, but it takes a lot more work and in the end may not be worth the hassle.
I'll stick with designing for users at 1024 resolution and higher, making fixed-width sites.