For almost 2 years Apple was the un-rivaled winner of the 30" display world.  This past January however, Dell took a shot across Apple's bow with the release of their own 30" display, the UltraSharp 3007WFP.  CNET puts them through the test in a side-by-side stand off of features and performance.  (linked below)

Comparing features and performance alone, Apple barely edges out the victory in this match.  However, if you were to weigh the flexibility of the displays (Dell rocks media card reader slots, audio-in, and 4 USB ports to Apple's 2 USB and 2 FireWire) as well as the costs of each, Dell would be a hands-down winner.  The Dell retails for $2200 compared to Apple's at $2500.  (However you can probably find slightly better deals on the Dell with a little effort.)

The LCD panels were unconfirmed as to their origins, but since the 2 companies' 20" displays use the same panel, it's wagered that the same applies to the 30-inchers as well.  I've personally got the Dell 20" display, and it's fantastic, and half the price of the Apple competition.  I think I could find it in my heart to give the UltraSharp 3007WFP a chance as well.  Donation line forms to the right.