Fixed width or fluid layouts?

I recently started work on a website that uses a fluid layout and it has caused me to think about the old fixed width vs fluid layout web design debate [for example, here].

I mostly like to use fixed width layouts because they just seem so much more readable to me but the website I recently worked on took up 100% of the browser window. During the work, I had a real problem convincing myself that the 100% layout 'worked'. I never used to have this problem but perhaps the larger monitors and screen resolutions we use now have made it more difficult for me to persuade myself that 100% of the browser window is a 'good thing'.

Perhaps I have become so 'fixated' on fixed width layouts and I need to re-educate myself about fluid-type 100% layouts again.

I don't know but I think I need to look at a few good examples of fluid layouts to redress the balance in my own head....