i didnt know how it would look either. i do now. i have a 24" iMac and LCD ACD on my desk right now 
To make the height differential go away, would putting the NewerTech miniStack underneath the CD be perfect?
http://eshop.macsales.com/shop/ministack/
It's 1.5 inches high and it looks like an Apple product. Someone is going to make a nice chunk of change making a product that makes the two monitor heights match...
I am going to setup my iMac with my 24" Dell, then, if I use the second screen enough I will get rid of the Dell and replace it with a LED ACD.
I am running the same setup. I bought the LED Cinema Display to use with my MBP, but swapped it over to the iMac later. It's a great setup. The height difference is not massive, but I do find it a bit annoying. I just need to find a solution more pleasing than a book under the LEDCD.
My next step is to buy some speakers, though I am not as much of a hurry, as the iMac speakers are better than I thought they would be. Certainly better than those in the LEDCD. Still, I think I will be picking up the Logitech Z-5500 set to here in a month or two.
I am going to setup my iMac with my 24" Dell, then, if I use the second screen enough I will get rid of the Dell and replace it with a LED ACD.