I'm definitely in favor of cleaned chips. I think they show better & are more accessible to the un-chipped masses. I don't need my chips to be in pristine shape, nor do I need them all to stand on edge, but I definitely clean up every singleton chip that lands in my collection, and have invested about $200 into a ultrasonic cleaner & related gear when it comes time to clean used chips en masse (I've put over 12k chips through it so far).

Here's some before and after pics I took of some bargain bin fractionals I picked up at the convention last year. I'll take cleaned every time!