I think both "무척" and "매우" is often found in written, and "매우" is seldom used these days compared with "아주","정말".
In spoken we prefer to use "아주","정말","진짜".
(There might be a slight difference among them in nuance or connotation,
but in most cases they are quite interchangeable)
For example,
오늘은 날씨 정말 좋다.(In fact, it's raining now in Seoul.ㅠ.ㅠ)
= 오늘 날씨 진짜 좋네요.(more casual than "정말")
= 오늘은 날씨가 아주 좋다.(more casual than "정말")
You can pick one of them up because it's just a matter of a personal preference.
As for "무척",I have never spit it out when talking with others.
^________^