In my current development box at work I am blessed with a pretty nice dual-head video card.  Off it I run my vintage Gateway VX900 19" CRT plus a shiny new Dell 1704FPT LCD.  The LCD lives on DVI and the CRT lives on 15-pin VGA dsub.  All pretty normal.

A few weeks ago I decided to try rotating the LCD into the vertical orientation and I have to say I'm hooked. 

What I like most about it is some windows like browsers, Acrobat, Word look better vertical however some windows are more useful horizontal, like Outlook, Visual Studio etc - this way I can keep both. 
 
I am convinced that there is less eyestrain reading documents in the vertical orientation much like we do with hard copy because the eye has a shorter distance to scan left to right.

Now my desktop is thus:





To be fair, some things suck about it:

• Some apps just don't know what to do, and pop-up a window too tall on the horizontal window or too wide on the vertical window.
• My CRT can do higher resolutions than 1280x1024, but it feels goofy dragging windows between screens and having them shrink and grow.  Freaks me out :)

If you have a vid card + driver that supports it, plus the right hardware I say try it out.  You might like it :)