Sullivan & Cromwell's interviews are pretty straight forward. I heard that once you get the callback (probably a large combination of grades and personality), you've pretty much already gotten the offer. I.e. it's mostly a formality, unless you really screw up.
Sullcrom's culture is very white shoe, stuffy and formal. They definitely treat their lawyers with respect though, and provide an army of staff to help them. That doesn't mean that it makes one's life any easier, since there's always an abundance of work. to go around.
Really top notch work quality. I spent a year here and my summer. When I compared the work quality with my counterparts at other law firms, I was very surprised to see the degree of sloppiness in work.
Sullcrom always provides a lot of opportunities to get onto high-profile deals. There's no shortage of flow, however one needs to understand that Sullcrom is a NYC-driven company. There's lots of satellite offices, but the work seems to be mostly sourced from NYC.
Benefits are pretty crappy, IMO. Instead of getting stipends for bar-study, Sullcrom gives you an advance, which you pay back during your 1L year (at least this was the case when I was interviewing).
No 401k matching. They do cover bar fees. Health insurance used to be 100% covered for the employee + spouse, but this stopped before I left.
20 days vacation accrual, which is pretty standard in service industries, I think.
A great place to spend maybe a year, however the burnout rate is exceedingly high. I was always surprised by the amount of turnover, which seemed extremely high, even for a law firm.
Beware satellite offices, which are subject to trickle-down governance from NYC.