I have had similar issues; I bought a space grey model today, and when I got home, immediately when typing in my password I noticed the "1" key just didn't feel quite right. The new keys are supposed to 'click' and register no matter where you press them, and this happened for every key other than the "1" key consistently on mine. The 1 didn't have the same feel or accuracy as any of the other keys.
I went back to the store and swapped it out for a different Macbook, and while this one is much better, the "Delete" key is now the one I notice that doesn't feel quite the same as the other keys. However, since there is no problem with the key registering no matter where you press it, I suppose I'll be able to live with it.
Pretty surprising that myself and others are having these issues; Apple is known for superior quality control but I suppose this is sort of a hard issue to diagnose/notice in the factory. Does anyone have any experience getting an individual key swapped out at the Genius bar for these new Retina 12'' MacBooks? It would give me peace of mind knowing if the delete key or some other key falters in the future that I'd be able to get it replaced without it creating a bigger issue.