I watch the show and like it. So do millions of other people, which is why it has the 9 PM Tuesday slot on FOX. I like musicals and Broadway and stuff, so it works for me.
It's a musical, so of course it's a bit corny. Plus, it takes place in a high school and the target audience is the teen demographic, so of course it will seem immature to older audiences. It has a feel-good message and basically addresses the importance of arts education, which I think is pretty cool. Sometimes they take risks with the music, but they have to include mainstream stuff like Kanye and Gaga in order to hold the attention of the young viewers. From the comments in this thread (and from talking to friends) it seems like the show appeals more to women than men. It might be hard to figure out the story line at this point since so much has happened with the characters in past episodes.
The funk episode wasn't very funky, but kids these days probably don't know what funk is anyway. "Give Up the Funk" and "Tell Me Something Good" were cool. They had pregnant girls dancing to "It's a Man's World" (more soul than funk, right?) which I liked (the performance more than the song). They have to include songs like Beck's "Loser" so as not to offend the funk hatterz. Even the Gaga episode wasn't all Gaga. The Madonna episode was my least favorite. I'm 22 and Madonna seems really old school to me, so a whole episode based on her songs had me lost.