I don't miss HS because I'm in college, and even just talking about academics, it blows HS out of the water.
There are a few things I actually do miss. Gym rocked pretty hard because we basically convinced the teacher to do dodgeball every single class; I don't think I would be able to get a good game of dodgeball going like we had in those days. Everything I needed, from cafeteria to library, was in the one giant building and I didn't need to walk around a large campus. Really got a sense of events and holidays just by walking down the halls; Halloween at college is pretty boring since everyone only dresses up to go to parties at night, so you don't see kids wearing costumes in class. Sharing almost an entire schedule with friends so group projects didn't such for any class.
I think that's about it. Well, I was also less lazy in HS since it was 5 days a week, I had to get up early every day, and freedom started late in the afternoon. My college schedule is so much better than anything I've ever had in HS.