The TKL (ten-keyless) design doesn't include the number pad (which is a pro for some, yet a con for others). This makes the board more portable as it is about 20% shorter. It is also more ergonomic when using a mouse - instead of reaching way over to the right (for right handed users), you can...
While not RGB LEDs (each LED is a single color - there is no way to change the colors from their rainbow configuration), there are different settings for the backlight. There are 3 brightness levels, and 6 different modes (breathing, two reactive modes, and a couple others.
The keys are concave on top, helping guide your fingers to the center of the keys which prevents your hand position from changing. There are grips on the bottom to ensure that they keyboard doesn't slip when you're typing.
The keyboard has a USB port as well as a headphone jack. This makes plugging/unplugging frequent peripherals easier, expands the number of ports you have available, and can allow for better cable management.
Razer makes their own switches - orange (similar to Cherry MX brown) and green (similar the Cherry MX blue). They aren't help up to the same quality assurance other switch types are, and there are many claims that switches aren't uniform (pressure and actuation distance is different between