Most of the music at the festival itself is Techno typically. There is typically a good amount of house there, but the amount of techno outnumbers every other genre combined at the festival it seems. I don't see there ever being any Happy Hardcore at the festival itself, but there are sometimes afterparties that have that type of music. Detroit is a Techno city and will always be...
Check
www.detroitluv.com for info on all the afterparties...almost every one is posted on there...
I've heard of a lot of the DJs on the lineup, but if you're not into Techno, its not surprising that you wouldn't have heard of a lot of the names on there. If you don't know an artist, look them up on the web and hear what they play, you might find some folks that you like that way...