Just to let you all know that the new iPad 3 has a different sleep wake function than the iPad 2 and some third party iPad 2 cases will not activate the sleep wake function.
There is a magnet in all smart cases that activates the sleep wake. It's about 7cm down from the top right side of the iPad. In the new iPad 3 the magnet has to be "negative" side face down to activate the sleep wake. With the iPad 2 it didn't matter what way round the magnet was facing.
So you will find some cases will work and some will not work depending on which way round the magnet was put in. This can change on a case to case basis with some manufactures - such as Yoobao.
All Apple own brand Smart Covers work as they all have their magnets facing the same direction (as you would expect). We have updated our product