This isn't a direct answer to your question, but this brings up a point I've thought about for a little while.
The Cinema Display is, in my opinion, the ultimate sacrifice of functionality on the altar of design. Part of why I think that is because of the buttons on the side. For one thing, you can't see them without physically moving to look at the side of the monitor -- what kind of usability is that? Second, if you're insane enough to spend the money to get two or more of these things, and you put them up next to each other, you're not going to be able to access the buttons on any of them except the rightmost. Dumb, dumb, dumb. I like to be able to quickly turn my monitors off, thank you very much. Third, although this isn't really related to your question, their stupid cabling that forces you to have your power outlet within like five inches of your DVI connection on your computer -- let alone the fact that the monitor has only ONE input, where every other LCD monitor on the market that costs more than $150 has at least two inputs. The Dell 2007WFP may not be quite as pretty, but it has the same panel inside, more adjustments, lots more inputs, and you can almost get two of them for the price of a 20" Cinema Display.
OK sorry, that rant's over.
To directly address your question, although I don't have a Cinema Display or an Apple notebook, I usually put my secondary display on the left of my primary display when I'm using OS X, but I prefer the secondary display on the right when I'm using Windows. On the rare occasion I've hooked up another display to my laptop, I actually have the display above the laptop screen, not on the left or right.