I ordered my late 2012 iMac right after the Apple event, got those ugly, disturbing (especially as the mac is used for graphic design work) dust smudges in corners pretty soon, I thought I could live with it but decided to send it a week before the end of warranty, a year later it started again, no more warranty, and it annoys me since then. I vacuum regularly and obsessively and have an air purifier and ionizer in my room.
By now I thought everyone knew that if you get iMac you will get these sooner or later. And it was a very well known issue before, I wanted to get iMac in 2011 but because of this I waited and hoped for a redesign. It was such relief when they introduced it laminated, I ordered right away... What a lamination that is and why Apple don't give a f for so many years?