My 2 cents worth...I actually think that HS is socially worse than Uni is (what I've experiences so far). In High School, you're pretty much pigeonholed into a certain group from the age 12 or 13 and most likely, hang out with the same sort of people. I was terribly shy at the beginning of High School, and managed to find a group of nice people to hand out with...fast forward 5 years and although the dynamic of the group has changed a bit (a few people came, a few left), I was still essentially in the same group. Don't get be wrong, all my friends were great people, but I felt that I couldn't meet new people because everyone was so deeply locked into their cliques. At uni, it seems to be a lot more flexible, and the vast majority of people are more open to becoming acquainted with new people.
As for friendships, in High School it was much easier but it could happen in Uni too if you take initiative. I've have been lucky to be invited to hang out a few times so far, but I know that you can't always rely on other people. So, if you feel that you really click with someone don't be afraid to take initiative and invite them for coffee. Chances are, they would be more than happy to come.