MAXhard increases hardness to 20 or so on Rockwell scale. They are much harder than standard forged receiver.
The process makes the outside hard, but leaves the inside of metal just like a normal forged reciever. If it was Rc 20 all the way through, it would be brittle. This gives you the best of very ahrd finish with softer metal inside.
For those who think forging is so much better than cast, they will LOVE MAXHard because it makes is that much better than the forged receiver.
The receiver is also darker than a normal forged receiver, which is pretty hard to do, as the forged T3 receiver is very black.
Is it worth it? For most people no. For those who are want to be GI Joes, get it. If you want to put a .50BMG upper on your lower, get it. If you want to spend money, get it.