Much more interesting to me was their shading of hair. First of all, they put a lot of details into the hair, but the really interesting thing here is the shading. The highlights are done with gradients, not something you see every day. Additional to that, they use tons of gradient shading in the first episode on other things too! Lines are generally drawn fairly thick, which I like. Characters still look like they squint all the time with wide opened eyes though.
Gradient hair is done all the time these days, and it usually looks awful. What makes the use of it in Mysterious Girlfriend X different is that it's a combination of gradients and traditionally drawn hair highlights.