Sammobile have just discovered this specification from inside the Samsung GT-i9300 Service Manual. As you can see the S3 does support a home button and will apparently have a new type of Super Amoled screen which is going to be 4.8″. According to the manual the Processor speed is 1.5GHz which seems odd as Samsung have just introduced their 1.4 GHz Quad-Core processor. Also the promised 12MP camera appears to only be 8MP, but for capturing images on a device I find this is plenty. It is possible this is an early specification however so it could change again.