Yes, primarily the yellowing issue. The whole review section flared it up and the ratings dropped even more. I was left on the fence. Also, the shipping dates slipped all the way to January. So on one hand, I could spend $280 on a first-gen color e-ink Kindle and have it delivered next month and on the other hand, buy the iPad Mini for $300 right now.
I guess at the end, the shopping frenzy just caught up and made me go for the Mini. Though, as you mentioned, I am hearing about the yellow band issue for the Colorsoft being fixed. So maybe in a few months, I might test out the Colorsoft too.