Same for K-On!, Hidamari Sketch and many similar shows. They are based on seinen manga and therefore aimed for adults. However in the case of K-On! for example the adaptation managed to reach a wider audience than expected; it created a female fanbase too that the manga didn't have.
So while they serve for classifying stuff, I wouldn't give too much credit to this system. There are many exceptions and observations to be made in each case.
Madoka Magica is a very different case. As well as being anime original and therefore not having a preassigned label, the series at least (and I assume the movies) is aimed for adults simply because it's a psychological and violent show. The characters are cute-looking actually not due to this intention of attracting the audience with cuteness, but because the genre they are dealing with and deconstructing involves these kinds of designs. I don't believe this series appeals to cute, in fact it uses this as a tool to generate some radically different feelings.
It's interesting to see the ratings distribution of the film in the IMDB:
http://www.imdb.com/title/tt2194724/...?ref_=tt_ov_rt
It's average is an impressive 8.5, though it might fall as soon as more people vote (there are only 57 votes as of today). Note that there was one woman aged between 30-44 who voted for 1, she probably showed that stuff to her kids.

This guy liked the movie though he never watched serious anime before:
http://www.imdb.com/title/tt2205948/...?ref_=tt_ov_rt
Last edited by Guaporense; 08-23-13 at 05:22 PM.