I call bullshit. I've been using the Nude Ultra-Clear since the iPad first week launch, and it has been "ultra clear" all this while, zero yellowing. If you are basing your statement on your experience with the Nude on 3GS , they are not the same build material as the Nude on iPad.

Of course, if you start bloody smoking around the iPad with the Nude case on, any ultra-clear case will turn ugly dirty because of that.