While I don't have the Apple 17" LCD, I do have one from ViewSonic that is 17.4" (I know, less then 1/2" larger). I went with the ViewSonic for two reasons. One, I have always had EXCELLENT results from their monitors, and the same with their support people. Two, the cost. I got the ViewSonic for under $900. I have seen Apple's LCD displays, and have to admit they are very nice. BUT, when I compared the two side by side, the actual screen on the ViewSonic was nicer. ViewSonics work great in any light AND they use standard connections (allows more people to use them).
If you don't have an ADC equiped G4, then I would lean towards the ViewSonic. Especially since they cost less $$. The ViewSonic model that I did pick up (VG175) has two video inputs, allowing you to connect two systems to it and toggle between the two.
Just something to consider/