It has nothing to do with size of text. It has to do with work surface area, and in the case of dual screens – organization ability.
That, and watching t.v and movies on my 20 inch wide screen is just gorgeous. 
15" widescreen laptop. I’m happy with it, but wish I knew a way to change the screen to “non-widescreen display”.
Maybe- I still prefer to watch movies from the comfort of a leather lounge. 
I did some work recently on 42" plasma screens with digital control units bolted to the back. It was much easier to just plug a mouse and keyboard into them, rather than remove the DCU. I can’t honestly recommend sitting a couple of feet in front of a screen that size though. I could never shake off the niggling fear that it would fall on me.
but can you do work or read a webpage on the other screen while you just idly have the boob tube on the other screen? During commercials?
… that and I don’t own a t.v
What kind of work do you do that two are more helpful?
I am not mhendo, but as a programmer, I work on one screen and use the second screen as my reference, I will have on-line programming manuals open on it, file displays or reference code. It is extremely handy. If I had a larger desk, I might even go with 3 screens at work.
At home, I do very little coding, so one screen is plenty and lets me keep my color laser on my desk. I prefer this setup.
My family room setup, allows me to use the computer and the LCD panel TV to ref an occasional D&D game. I have a small table and LCD panel that I drag over to the game table and I can keep my notes from prying eyes but at the same time display maps on the large 37" LCD in perfect clarity. The Computer also is tied into my stereo system allowing me to play Internet radio or MP3 library to anywhere in the house.
Jim
23" Benq LCD at 1920 x 1200. The contrast and screen quality is not quite as good as other flatscreens I’ve seen, but, hey, it was on sale at half price. 
19" flat panel. Bigger is better.
Well, What Exit has given his own take on it. Here’s mine.
First, i’ll admit that i don’t really need two monitors. I could survive with just one. I’m not a programmer, or a professional video editor, or anything like that. I’m a grad student.
For my work, i like to have two monitors because it makes it easier for me to take notes. I get a lot of information from academic databases, so i need a browser window open for finding articles and things like that. Many of the articles that i download are pdf files, so i need Acrobat open. I also like to have MS Word and my citation software, Endnote, open.
Reading the pdf articles and taking notes in Word or Endnote is easier if i can see both at the same time. Having Word and Endnote open in one monitor, and my internet browser and Acrobat open in the other, just makes life easier.
When i’m not doing that sort of stuff, i still like having two monitors. I do a bit of digital photography, and i also use images for the lectures i give to my undergrad students. When i’m using Photoshop, it’s nice to have the image area open in one monitor, and the toolbars open in another. Also, i like having my email in one monitor and my browser in the other.
There are other times when it’s handy. Right now, i’m trying to teach myself CSS for the internet, and i’m also dipping my toe into PHP/MySQL, just for fun. For those things, i have some electronic instruction books, and it’s nice to have the instruction book open in one monitor, and the programs open in another, so i can read the instructions and practice my coding without needing to constantly maximize and minimize windows.
As i suggested earlier, none of this is absolutely essential for me, but it is nice to have, and now that i’m used to it, i couldn’t go back to a single monitor. For my purposes, it’s also good to have an LCD and a CRT, because the latter still tend to be better at rendering accurate colors for digital photography (assuming you’ve calibrated the monitor properly).
By the way, for all the people who use multiple monitors, have any of you tried UltraMon? I’ve been thinking about getting it, and was wondering if it’s worth the $40.
In August I finished porting a 45-file FileMaker 6 solution (really an interlinked pair of soluions of 20-25 files apiece) to a 5-file FileMaker 8.5 solution, mostly rebuilding from scratch (too many nice newer ways of doing things) but definitely referring back to the old files as I went.
The layouts (i.e., screens, the GUI, with buttons and fields and other graphical elements) can’t be copied and pasted (or dragged and dropped) from FileMaker 6 to FileMaker 8.x, so to avoid having to create the layouts from scratch I ended up with a third version of the solution, a direct conversion of the 45 FileMaker 6 files to 45 otherwise-identical FileMaker 8.x files.
Having three screens was closer to essential than to merely convenient. Some days I’d have the layout I was working on open on the screen to my right in Layout Mode, the ScriptMaker in front of me, and a PDF of the FileMaker 6 script I whose function I was replicating open in Acrobat on the screen to my left. Other days I’d have the layout I was creating open in front of me, the FileMaker 6 version open on my left, and the converted Fm6-to-Fm8 layout on my right to drag or copy elements from as need be. The next day I might have the startoff layout on my left screen (so I can see fieldnames & etc), the target report screen open in a second windows on my right (so I can be reminded of the subsummary sort order and page setup requirements) and the script I’m creating for running the report there in front of me.
Given that I also had to read and answer email, browse the 'Dope (I mean, hey!), and occasionally manage files in the Finder, I really could have used yet more screens!
When I’m in Photoshop or other apps that have sprawlingly huge arrays of palettes and buttonbars, I have all that crap on one of the side monitors with the project or image in front of me, unobscured by floating detritus.
When I’ve got some task cranking along but need to jump back in and do something when a progress bar finally gets to its destination, I drag that window off to one side, so I can glance at it periodically but go on working on something else.
19" flat panel. I’d love to have dual monitors, but in a dorm room? No way. To be fair, I wouldn’t even have this if I’d had to pay for it; I’d still be on a 17" CRT.
17" LCD widescreen flat panel, coming from a 15" CRT. I’m still figuring out what to do with all the extra space.
A 23" Apple Cinema Display flat-panel monitor.
17" LCD at work, 24" widescreen LCD at home. I love both, but the widescreen is really nice cuz you can comfortably fit two things on the screen at once, like a Straight Dope window on the left and a YouTube video on the right. Also nice for movies and gaming.