Right. Cater to Lowest Common Denominator.
Or close to it.
I develop to 775 pixels wide max (leaving 25 pixels for the window borders), but my monitor is 1152 x 864 at home and 1280 x 1024 at work.
Plus I develop some sites to break apart for PocketPC, etc. - i.e. 220 pixels wide.
Plus there's those browsers that take vertical real estate for their crap.
But I keep it to 775 - even today. Although I've been strongly strongly tempted to ramp it up to 1000 pixels wide (I like round numbers, so I'd only be allowing 24 pixels), as the default for Windows (which used to be 800x600 with Windows 9x) is now 1024x768 and most end up at least there anyways.
Just IMHO