One of my best friends is an Ob/Gyn intern at Pitt, and I can assure you that the current intern class is extremely close-knit. My friend spends nearly all of her time outside of work with them. They plan something social as a group basically every weekend, and it is unusual for anybody to miss out on the fun. I don't think this same type of closeness exists between the upper levels & interns, but they do socialize between classes from time-to-time and the interns seem to get along well with most of the uppers (I have only heard about a couple that sound hard to work with).
Overall, I don't think my friend is unhappy, but I wouldn't call her happy either. She's working hard and frequently feels physically and emotionally exhausted. On the other hand, she feels she's working with amazingly talented residents and attendings and is getting great training, so she is content with her decision.
I hope that's helpful.
-BBB