It's a very unique lifestyle, to say the least. I think in first year most people (usually) enjoy university because of the lack of responsibility and the freedom and so on. By third year, a lot of people I've spoken to are longing for a bit more structure in their lives and in some cases are wanting to hang out with more mature people and so on. So I can definitely see where the OP is coming from.
My course is 95% girls and there's about 130 of us, so that's a LOT of girls. However, I think I've been lucky in that we're a good year group- most people are very friendly and there's no real bitchiness or anything.
I have to admit I'm one of those people who loves uni life and everything about it, but that might be because my version of 'uni life' isn't quite the norm- I mean, don't get me wrong, there have been plenty of nights out and crazy shenanigans and what have you, but I've made sure that alongside that and studying I did as much other stuff as possible- part time job, internship, radio show, squash, debating, volunteering, and so on. THAT'S what I love about uni life: it's the one time when you can do pretty much anything! And through these things I've been lucky to meet lots of lovely people. Add the fact that I adore my course and, well, it's been a good three years. The only negative is that campus life where I am can be a bit of a bubble, so I'm looking forward to actually living in a city next year- but on the other hand, campus life is probably one of the reasons why I've felt so at home here, as in 'real life', you don't bump into friends wherever you go. So I'm definitely going to miss that.
I will agree that group work is a PAIN and I'm very glad I haven't had to do much of it over the past three years. Putting people into random groups and hoping everyone will do their fair share just never works out.