I read an interesting post this morning on how the author wanted folks to consider the 800px resolution for their designs. He cites that although he has a large resolution, it doesn't mean that he's not also using other applications at the same time.
...But with 1900+ pixels, I keep half for the browser and half for other stuff. If you go with 1000+ pixels, it doesn't leave me with enough room for my other apps, and I've got to (ack!) scroll sideways. It's not as bad with the ball on the Mighty Mouse, but most people don't have one and it's not exactly effortless even with one... - Sammy Larbi
It's an interesting point to debate, as whilst on one hand I do agree with him that the potential for your audience to overlay multiple smaller applications is there, yet at the same time the benefits of expanding your resolution to accommodate more on screen can also be in an asset.
Screen real estate is a hard subject to nail as even if you're the best information architect in the world, you will still annoy someone with your chosen path. The trick is to figure out you collateral damage, in that what percentage of your user base is going to disagree with your design.
The easiest way to work that out is to do some basic research, check the statistics of your existing site (assuming you had one already) then ask them but do so in a way that doesn't draw attention to your intent - as humans are funny at times, they do one thing but say another.
Q. Do you think Coke is good for your diet...
A. Yes, it's terrible...
The intent was it's terrible, bad, negative, stop!. Yet they will drink coke.
Here is a tip, we are habitual creatures and if you can compliment our patterns of habit, you're likely to become less annoying.
Take this blog for example. Below is a graph indicating my resolution stats for this blog.
Would it be a good idea for me to go back to 800x600 resolution? If not what would you consider my ideal resolution.
Know your audiences technology limitations, know your customers habits and above all plot your approaches into a Risk Matrix.