My preference is a fixed-width layout.
- content is easier to read
- it's easier to scan page (looking for something specific quickly)
- the site will always look the same
- layout size is similar to everyday magazines, business papers, letters, etc (8*10)
- more control over design (eye candy)
With that said, a liquid layout is not wrong .. it just has to be handled differently.
On a photo(s) site, a liquid layout would work better. eg. showcase photos, etc
Other things you have to consider when designing an interface...
- server resources (memory, bandwidth, http requests) - an increase in server resources regardless of type will have a negative affect on user experience
- site's popularity (growth) - interface should be ready for growth
- dial-up members