The Razer BlackWidow keyboard line has now gone through 2 iterations and almost 7 separate models. While it is the only mechanical keyboard that Razer currently offers, it’s also one of the most well made out of their entire line. Some of the changes to the 2012 version include an expanded anti-ghosting set of keys, faster polling rate, and a branded upgrade to the back lighting.
Let's start with ghosting. When you press multiple keys at the same time on a standard keyboard, the computer can read only one key at a time. You can try it on almost any keyboard and see the limitations right away. Hold down two keys, only one survives. During gaming you might be strafing in a first person shooter using WSAD or queuing actions on the number keys in World of Warcraft.
The most extreme example is of course when a player is participating in a RTS game like StarCraft where the number of key inputs per second can often overlap one another. In these situations you will press multiple keys at the same time. The anti-ghosting technology has been extended to 10 simultaneous key presses, which means the Razer BlackWidow Ultimate can discern between 10 individual fingers/keys when you've got them all pressed down at the same instance.