OCI was very straightforward. I had the grades, so the interviewer basically said I was a shoo-in for a callback, and that I could email him if I had any questions once I got my list of interviewers for the callback.
I think most of the interviews for the callback were pretty cut and dry. Try to be a person, make jokes if you can, and have a consistent narrative for why you've studied what you did and where you want your career to go. I think my interviewers appreciated someone who was willing to not back down if asked follow-up questions, or who would clarify if their questions weren't fully answered. So be willing to be assertive, but otherwise, just try really hard to be a person (and not just a GPA).
Very "work-hard/play-hard." Everyone is 100% on top of their shit. For every research assignment, you need to have every case be in the jurisdiction in which they are litigating, otherwise it doesn't matter. Make sure it's exactly on point. But I think that's true of a lot of big law firms.
Otherwise, they really want to make sure you are a sociable and balanced person. The firm likes to take summers out, to make sure they can hang with the associates and still be at work the next morning without a hangover. And to be sure, the summer will probably be the best you've ever had. Work starts as an associate.
Most of the assignments I took were essentially research assignments. To be sure, Partners went out of their way to give me briefs to make sure I got feedback on my writing. And associates gave me research assignments on points of law that I'd be working in later. It was a pretty balanced amount of "Ok, do this so I can give you pointers," and "I need this done so I can turn it in to my boss." I was pretty happy with it, but I also recognize that life as an associate will be way different (and they do not try to hide that).
Seems great from what I can tell, but I can't really compare, seeing as I haven't worked for another firm.
I can't underestimate being personable.