I've been using dual 20" ACD monitors for about 4 years now, and was distressed that one of them, the primary monitor, died last week (looked like a dense graduated filter had been put over it - very dark at top, got lighter towards the bottom). Apple told me it wasn't economical to repair it.
Reading all the stuff in here and other places about how much better other brands would be, and knowing that the new ACD won't match my remaining monitor anyway, I replaced it with the Eizo CE210W. After calibrating the Eizo, I have to say I see very, very little usable difference between it and my old ACDs. The Eizo definitely produces deeper blacks, and at the calibrated points of w=119.7, b=0.14 that's giving me a higher contrast ratio (855) than the Apples did, but when you soft-proof the images much of that deeper black is lost.
The Eizo profiles more easily than my ACD did (got it first time, whereas the ACDs took a number of attempts), but I have to say it wasn't worth the extra money. I could have bought two 20" ACD's for not much more expense, and in retrospect that's what I should have done. The Apples look a lot nicer too!