Hi Bruce,
Personally, I like two monitors. A couple friends have the 30’s and I don’t see the point, just a giant place to fill with clutter. Might as well just get a 32″ or bigger plasma display if you want big. But the biggest disadvantage IMO is that if you’re working in HD and want to use a CD to monitor, with the 30 you’re toast for everything else, timeline, tools, bins etc. all gone.
I have a 23″ CD and a 22″ Samsung, so when I want to see HD full size, I just change the view to Cinema Display Full Screen and that fills up the Apple display, leaving the Samsung for everything else. Works great.
I also do a lot of AE and I am in the habit of putting my comp window on the left monitor, so my timeline can be deep. I suppose that could be arranged on a 30 but I just feel more comfortable with two screens.