I absolutely love my 460. It could use just a little more muscle, but everything else about it is a freaking dream.
From what I understand the 560 is about 30% faster. Yes, it's a fantastic card for the price. And the MSI cards are probably the best of that gen. The Gigabyte Super OC are great too, but I had heard bad things about the 560 series regarding reliability, when I was in the market. About half of the reviews reported failing or glitching out cards, so I went with the 460 instead. So really look through the reviews, but keep in mind the posted date, because the card may have had a new revision with fixes.
EDIT: I'm suprised you're not going with the 'Ti', or the overclock series. These cards can overclock like proabably no other. I like the factory overclock because it's gauranteed. Binned chips.