Personally, I hate slimcases (almost as much as those cardboard "snap cases" that were popular in the late 90's). They're just too flimsy! The point of the amray cases is to protect the discs, and to display the cover artwork. Both purposes are reduced with the "slimcases." These sorts of things are fine if you're putting burned discs into them or for temporary storage, but for classic movies you're displaying on your shelf? No thanks. I didn't mention the slimcases, because the ones I saw were standard size, but I have since seen the "slim" design. Frankly there's just no reason to do this except to save production cost. But is Lucas that much of a cheapskate that he has to skimp on packaging for what he supposedly considers his magnum opus?
So I wouldn't consider the use of slimcases a "special bonus." A person could reprint the covers and place their existing discs into slim cases if they wished (though I guess then the cardboard sleeve would no longer fit). It just feels "cheap." Perhaps treating the Prequel Trilogy like bargain bin software is most fitting? :P