The QWERTY layout was designed in the 19th century to allow typewriter salesmen to easily type the word "typewriter" and to prevent typebars from sticking. We've been stuck with QWERTY ever since. Colemak is a modern alternative to the QWERTY and Dvorak layouts. It is designed for efficient and ergonomic touch typing in English. Learning Colemak is a one-time investment that will allow you to enjoy faster and pain-free typing for the rest of your life. Colemak is now the 3rd most popular keyboard layout for touch typing in English, after QWERTY and Dvorak.
The promise of typing faster is not true, at least not for me. I type exactly as fast in colemak as in qwerty (110 wpm). However, colemak does feel more comfortable. Colemak is much easier to learn than dvorak (I reached the same typing speed as I have in qwerty in about a month). I stopped using qwerty that first month to really acquire colemak, but I have since been able to type in colemak and qwerty interchangeably without any problems.