Fingers of Steel
I'm assuming they supply replacements in different colours so that you can pull up your keys most used in game and give them a slightly different colouring to make it easier to distinguish. Either that or they assume you're so heavy handed you're likely to wear them out in a matter of months!
Talking about heavy handed, this is a keyboard based on the popular Cherry Mx series switches underneath the laser etched keys. These ain't no micro-switches like your momma uses! These babies need a solid depress in order to make the connection, which is great because your number of accidental keystrokes is reduced significantly.
The switches themselves are rated to approximately 50 to 60 million keystrokes, so there's no chance of wearing them out before you have developed carpal tunnel and your fingers have been reduced to stubs.
Moving on to the wrist rest; I want other manufacturers to read this and take heed. This is how you do a wrist rest! - Notice the embossed logo is off to one side, well clear of the part where your wrist rests on the slope. When the rest is not in use there are a couple of tabs that can be inserted into the back of the keyboard and locked in place to keep the profile of the keyboard flush.
Removing the tabs, we can see a solid clip device that holds the tabs in two places, not just one, adding to the security of the system. When the rest is clipped in place and the tabs stowed with the replacement keys, you will notice it flaps around a bit. There is a very good reason for this; it folds back underneath the keyboard itself to be stowed when in transit. Very clever!