If you're looking at Ipad 2 cases for your 3rd gen Ipad, pay attention at 2:25 in the now famous Vietnamese unboxing video:
http://www.youtube.com/watch?v=9FCm_ggEhPQ&feature=player_embedded
You'll clearly note that the Ipad 2 lens is smaller and - while aligned closer to the right side of the power button - doesn't extend past it. On the "New Ipad", the lens hole is larger and it's alignment extends past the edge of the power button. So even if some vendors are saying that their cases have enough give to deal with the minutely thicker case of the new model, it looks like there's probably going to be issues with camera alignment with the holes in the cases.
http://www.youtube.com/watch?v=9FCm_ggEhPQ&feature=player_embedded
You'll clearly note that the Ipad 2 lens is smaller and - while aligned closer to the right side of the power button - doesn't extend past it. On the "New Ipad", the lens hole is larger and it's alignment extends past the edge of the power button. So even if some vendors are saying that their cases have enough give to deal with the minutely thicker case of the new model, it looks like there's probably going to be issues with camera alignment with the holes in the cases.