> Is it an everyday word?
I think it certainly is used enough for it to be a popular parlace slang term most speakers will be familiar with.
> When is it good to use "" (out of fashion, boring)?
It helps me think of it as an approximate translation of _lame_ and how speakers use that word in English. There might be a slight caveat in this though, in that seems to be directed more at what is considered by the speaker lame _fashion_ and not exactly _attitude_ per se, as suggested by this answer in Chiebukuro asking about the difference between and . So this would include "out of fashion".
For the general meaning of "boring" it is a harder fit in my opinion. I'd probably be using instead.