I'm a listener and appreciator of all kinds of rap.  Cassidy to Cunninlynguists to Chief Keef.  Chief Keef is hype music.
For the most part, he's in the same category as Waka Flocka, 2 Chainz, Trinidad James, Future, Juicy J... etc.
The type of music you listen to when you want to get pumped up, or you're in a great mood (or a bad mood actually.)
I think 99% of people that listen to Chief Keef and the other rappers I listed, would say that the lyrics are garbage.  They don't offer much to make the listener think intellectually.  But there is a lot there that is intriguing, it just depends on what you like.  The beats are usually sick, the choruses are usually catchy, etc.  It's not "good" music per se, but it is catchy.
That being said, tell me these vids don't look like a good time:
Still don't think I'd go to a Chief Keef show though...not with his record