I'm old school and when I started to learn Japanese it was for the "good" reason. Love of the culture and will to go there to work.
After a few years, the manga/anime wave invaded the West and we witnessed an increase in registrations (university) of about 200% or even more with overcrowded classrooms. (when I started, there were days when I was alone in the class room with the teacher!)
All these new students came for the same reason: Mangas are cool! (and interestingly the number of attendance dropped radically after the second year...)
To answer the question: I see more and more students (and questions from beginners here) using manga-like sentences. They understand the meaning but they don't know how and when to use it (usually they shouldn't use it at all)
We could see 20 years old boys talking like 10 years old kawai girls or 20 years old girls talking like yakuzas! Needless to say they looked pretty stupid during their home-stay in Japan.
Except these 2 extremes (which we witnessed quite often), students coming from a manga background had more vocabulary than "normal" students and learned more easily new things (although keeping their bad habit of speaking like a girl, a cute kid or a yakuza)
Their understanding of grammar and knowledge of kanji was generally very poor though.
Avoid learning from manga until you're at a level where you can make the difference between what you hear and what you can say.
Tv, drama and radio are ok though. They show you a lot of real life use of the language.