After the iPad 3 event invite didn’t show a button, some were quick to come to the conclusion that there wouldn’t be a button on iPad 3.  We think this is highly unlikely. Among many other reasons, there is one in every leaked iPad 3 part, as shown by these digitizers on today.

Also we see both black and white colors represented.  We had originally heard that there might only be one color of the base model iPad 3 but a few hours later, we found the new part numbers which indicate both colors would be introduced. Another image below: