From what you see posted on forums, it appears that Apple is much more careful about shipping a "perfect" LCD with no backlight leaking and no dead pixels.
With Dell it appears about half the monitors send out have that to some extend. Depending on how picky the user is and what he does with it (who cares about backlight leaks in MS word?) you can send it back for replacement as often as you wish, at least that is my understanding.
The 30" requires the dual-link DVI video card.
The more appropriate comparision would be the Dell 24" and the Apple 23" inch. Both run at normal video cards and are similar in spec. The Apple one is IIRC $2000, the Dell one $1200 and you can use lots of rebates with the Dell one. The Apple display will give you more quality control before it is shipped to you, see first sentense.
Alas, if you have a SLI setup and want to continue to use it, you cannot use the Apple 30", period.
Personally I would like to have a 1.67GHz 15" Powerbook with the dual link DVI option and the 30" display. But that is a $6000 combo. If you compare that to a FX-55 with SLI 6800 Ultras and two Dell displays it is not really economical.