[Princeton]

There will always be sites/designs built for 800 resolution.

800 is idea for reading
800 is the closest thing to letter size office paper - people are accustom to reading in this format eg. letters, books, magazines, etc

you can always offer a width option for those who prefer wider layouts

nothing wrong in creating a design targeting higher resolutions..
you just have to make sure that your reading area is equivalent to a letter size format (it's easier to read) ..

I know of some users that actually surf while their browser window are completely open on a 1600 resolution. On a forum with long content (on a liquid layout) this would mean that they are reading from extreme left to the extreme right - bobble heads. This is what you need to address.

Another issue that needs to be addressed..
if you create a fixed 950px layout ... you have to be aware of your ad placement eg. placing ad on right column

if 14% of your users are using 800 resolution .. than that's equivalent to a possible 14% decline on ad revenue (they will not see the right column unless they scroll horizontally)

TIP: for those with 1600+ resolution monitors .. surf with 2 windows open .. you get a whole lot more accomplished - faster.