It’s often found in the classroom, and spoken by people who not only don’t understand, but don’t want to make an effort to understand. I don’t believe that for everybody, and the reasons for the lack of interest vary from person to person and class to class, however I do hear a lot of teachers complain about students using the word. That, and it’s partner in crime 面倒臭い (めんどうくさい – pain in the arse/bothersome/etc).

The two are often viewed as words that represent the general trend towards laziness many older Japanese sill be happy to complain is successively plaguing each new generation.

So, though 微妙 itself is a word, and seemingly useful, I myself take care not to overuse it, use it when I mean it, and to watch my apathy meter.

Though, if you don’t care much about this sort of stuff, 微妙 is definitely the word for you =)