Actually, it's not supposed to slow you down. It's supposed to make sure you're normally hitting keys that are far apart, which means the hammers won't interfer

Actually, it's not supposed to slow you down. It's supposed to make sure you're normally hitting keys that are far apart, which means the hammers won't interfere with each other. QWERTY is a pretty good layout because of it. The next letter you try to type is rarely in the domain of the finger that just pressed down, meaning you can line up a number of keys to be pushed at once. In the Design of Everyday Things, Donald Norman talks about keyboard design a lot. QWERTY is really good, so switching to layouts that are only slightly better (dvorak) end up not being worth the time and effort.