Ceran:
As someone with a lot of experience with Ceran cooktops, I feel that these tops are easy to clean.
The catch is that one must actually clean them, and most people nowadays don't do that. The burned-on black circles at each burner position that David (capecodlaundry) alludes to are a common sight on these tops, but in my opinion, it's laziness, not a fault of the technology. Scratching can be minimized through the exercise of reasonable care, plus using the cleaner (which has silicones) daily; the silcones protect the surface to an extent.
If you get one of these ranges, you have to get the cleaner, and you have to use it. Any renter who doesn't should end up paying for the range, in my view.