Actually it is a standard QWERTY keyboard, with rubber dome switches but this one happens to have a much lower actuation force and distance than most switches, with a soft, cushion-like springy feel at the bottom. Someone used to "better quality" keyboards such as mechanical ones would probably find the keys too loose and wobbly, but I've found that the loose feeling helps when you just want the keys to go down as quickly as possible, since at those speeds it's more a process of hitting keys without conscious thought and hoping they register rather than trying to sense their feedback.
I have tried mechanical keyboards, and for the longest time I used a clicky one with blue ALPS switches, which has a nice tactile response to the keys, but was not able to exceed ~130WPM with it - the clicking was actually distracting and I felt like I was waiting to feel the key switches actuate before moving on...
(Many of the fastest typists on TypeRacer and one of the well-known, Sean Wrona, use QWERTY so I don't think it's a big disadvantage in terms of speed.)