We have Corian countertops and the Corian 1/3-2/3 sink integrated sink. Our house is about a year old and we haven't had problems with scratching at all. I didn't want granite and the Silstone color choices our builder offered weren't to our liking.
How do you like the sink? That is the real drawing point for me. I keep thinking that 1/3 2/3 splits it up too much. What side is your disposal on? The smaller side? I guess it really is just a mater of getting used to it. I have always had a single big sink.