I purchased the Eizo ColorEdge C240 about a year ago as an upgrade from an old 21" Formac Gallery LCD display. I also have a year old Dell FPW 27". I also switched from a Dell Precision workstation to a new Mac Pro 8-core workstation so I have experience with the ColorEdge monitor on both WinXP Pro and OS X platforms.
The ColorEdge is simply the best monitor that I have ever used. According to Eizo, a big advantage of the ColorEdge is that the color calibration is done on the hardware inside the monitor which means that the full color bit resolution of your computer's graphics card is available to drive the display. With the Dell and other monitors that rely on color calibration on the graphic cards look up table, you are compromising color bit depth to achieve calibration. This is theoretical, but it makes sense.
I my case, I noticed when using Eye One to calibrate my Dell monitor, I had to manually lower the Red and Green channels using the display hardware adjustments in order to get the base luminance to the proper values. Although the Dell wide format LCDs are excellent, they are way too bright at the factory default settings for color critical operations like Photoshop.
I did not have any problems at all calibrating the ColorEdge with my Eye One colorimeter. The ColorEdge has it's own calibration software that works with a variety of colorimeters including Eye One.
Recently it was made public that the Apple Cinema HD displays are not capable of 24 bit color resolution and that they use dithering to simulate the full range of colors. This may explain why the Apple displays appear a bit coarse as compared to the Eizo. Of course, it could be my eyes too. According to a friend of mine who owns 2 Apple retail stores, Apple is supposed to be working on a complete replacement of their existing HD displays with a higher native color bit resolution. We'll see.
I love my Eizo display and I think that you will too. I just only wish that Eizo offered a 30" model for more screen "real estate".