Summary: I've owned the Apple Cinema 30" display for several years now and I kept Applecare on it until the warranty ran out. The display is beautiful and provides a ton of real estate on a single display. However this display did not age well. It now has a problem refreshing the screen quickly enough so there is a bit of ghosting that goes on. I've also noted some variation of brightness along the edges. If you get one of these and plan to keep it awhile get Applecare.
Summary: I use the Apple Cinema 30-inch display at work along with two 24" NEC Multisync 2490WUXi displays. Our systems are beefy HP workstations running Nvidia Quadro FX4800 cards. We use our Apple monitors as essentially a 3rd display for extended desktop space. In that use the Apple's seem to perform well with a few notable exceptions. Mainly these monitors have 2 reoccurring and annoying problems. The first is the well documented "dancing pixels".
Summary: LCD monitors inherently can be manufactured such that they end up with a few dead/bad pixels. This shows up as a colored dot on the monitor when certain colors are displayed. Apple needs to do the right thing and take a stand on quality control. Samsung has recently adopted a 'no bad pixel' policy on their monitors and Apple should do the same.