I know that 1mm is a huge span in terms of engineering and sci-geekery, but in the real world of human hands and what we hold to read, 1mm is invisible.
Reading about the thicker iPad3 always makes it seem bulkier. A descriptive like "barely thicker" is apt.
I guess that makes both rumors - that it's thicker then the iPad 2 - and - its the same thickness as the iPad 2 - correct.
The metal frame might be < 1mm thicker, however, if they use gorilla glass 2 - or the display is actually thinner as has been rumored, then the glass will be flush with the metal frame in the iPad 3 - currently it's raised < 1mm over the metal frame.