To this day computers ship with the same keyboard shape and key arrangement that was invented for the typewriter in the 1800's.
One of the silliest things of all is the dedication of both thumbs to the space bar. In general, the user only uses one thumb to press the space bar at all. This means that an entire finger (read: 10% of your fingers) isn't doing anything at all. Ever. Wat?
Initially keys were offset because keyboards were mechanical. This forces some of your fingers, such as your left hand index finger when typing the key directly above, into uncomfortable positions. It would be more optimal to have keys arranged in straight grids.
The Qwerty keyboard layout is known for its first sequence of characters on the top row. Imagine this: if you pulled all of the letter keys off of a regular keyboard, put them in a bag, shook them up, and placed them all back on at random, the new layout would more often than not be more efficient.
"But I already know qwerty."
I challenge you to seriously consider which of the following you would rather:
Let's say you are 25 and you live to the ripe old age of 75. Assuming that you don't use computers on the weekend (yeah right) we are looking at (365x5/7)x50 days. That comes out to a little more than 13,000 days. If you gain something, even a little bit of something, doesn't that make it worth it?
"What if I have to use someone else's computer?"
I can personally attest as someone who went cold turkey on Qwerty in 2007 to how little this actually comes up. Assuming the first point is true and you already know qwerty, learning a second layout is like learning a new language. You will always still be able to use qwerty.
It took me about three months to master the new layout. This is apparently much longer than usual. The people I know that switched took much less time than I did (two to three weeks).
I find that the real benefits to switching are the increased comfort and accuracy rather than the typing speed. In practice, typing speed matches the speed at which you think the words you are typing. The amount of backspace key presses really does decrease quite a bit. The comfort will speak for itself.
I recommend learning Colemak. It is supported out of the box on all operating systems.
I use the Dvorak layout. If you've heard of alternative layouts in the past, this is probably the one you've heard of. I recommend Colemak over it because Colemak is a little bit better.