After being almost dead against big monitors (I didn’t see the point given how close you sit to them anyway), low prices at play.com convinced me to get a new 19″ widescreen monitor. I am happy to say I was completely wrong and that the extra space is fantastic.
While finding a decent wallpaper for my desktop proved tricky, everything else is great. 1440*900 resolution lets you have a 1024*768 browser and enough space for any other active tasks that you might have, such as instant messenger windows. I recently bought Grand Theft Auto: San Andreas for the PC and playing it widescreen makes quite a difference to the views, particularly in the wilderness between Los Santos and San Fierro.
The one thing better than the wider screen is keeping the old one in a dual-screen set-up. You get all the benefits of the larger area, plus you can have one monitor dedicated to passive tasks (like IM contact lists, media players, bittorent clients) such that it works as an information display at a glance. I highly recommend the extra space to anyone.