I think its great for web design...you could have one monitor at one resolution, and the other at a lower resolution to keep check that your site you are designing works even in low resolutions and still looks cool on high resolutions...
That and you can watch a DVD on one screen while typing a paper on the other without switching between the two...
Graphics professionals also use dual monitors when using say Photshop...they use one monitor for the actual image they are working on and the second monitor for all the tool's and palates...nice not to have all that stuff up there in your image while you are working on it.
Ok i have a Gainward GF4 4600ti Golden sample and i'm using a dual monitor system for video editing but i also watch DVD's and play games and it don't see any performance hits the only difference i saw was in my bank balance But to be honest if i wasn't using it for Video/photo editing i would only use 1 monitor.
Yes, you could play a game/movie on one and surff the net, watch your temps, etc on the other You could also have the same image on both or have one image span across the two either from left ot right or top to bottem
I have been using two since july (19" trini and 17" trini) and love it. I cant do without it now. I feel way too confined, almost clastrophobic . Its nice for webbrowsing (multiple pages), monitoring an IM conversation (or two), or watching a movie or video while web browsing or doing real work (yah right). Its nice for doing general windows work (file moving, viewing, ect) and generally its just cool. I mean, how can you NOT like to have double the screen space. Not very useful for games, but i dont think there is much performance hit (maybe a little).
I started using two not so long ago, its cool...my main use is to have winamp or something on second whilst ingame on the primary, so in games like sof2 (need a sepcial thin to make it minimize) you can just pop across and chnage playlist or whatever without stupid downloads etc...
performance hits werent registerable to the eye (if there even are any).
but I have done the dvd on the extention and working the other thing which I love
btw - anyone know how you get mirroring to work under a hardware accelerated environment?
Two monitors is also popular with video production. When editing a video you will tend to need much more space then one monitor can provide. We have a video production box at our school with two monitors. I am of course banned from using it, because I'm not in video production. Sometimes if the tech guy isn't there I move the login screen back and forth between the monitors.
I used to use two monitors while programming. Much like Video/HTML editing you have one with your code and have the app/intranet(internet) page in the other... or SQLServer... it tends to increase your productivity. One of my old bosses said that when we finished the project we were working on(I left before we finished) he would get two monitors for everyone because it sped up our development times.