I've had to 0004 units and one 0003 unit.
My first EVO was 0004, got it in 12/2010.
My Second EVO was 0003, got in 4/2011. I sent it back because of a defective power button.
My third EVO is 0004, got it in 4/2011 as a replacement for the defective 0003 unit. My first EVO was the best of the bunch. I never had a problem with it. I sold it to get an HTC Arrive. That was a mistake. The Arrive is a good phone, but not worth selling the EVO for, in my opinion.