I had an offer at Cravath and went to work at Kirkland instead. I didn't really like the culture at Cravath and the benefits at Kirkland seemed more impressive.
Cravath is a good firm, but I think working for one partner for 18 months is tiresome and potentially disastrous. I highly prefer a free-market system where I have some control over the growth and development of my career. Additionally, once you finally master a particular areas or case, after 18 months you move on to a new case/partner where you'll again start from scratch. It seems like a highly inefficient way to train attorneys. Not to mention, my friends at Cravath privately have told me how insipid working there really is. ]
Look Cravath is prestigious, but no one gives a damn about associates. Unless you're a partner, you're not going to impress anyone saying you're an associate at Cravath, Swaine and Moore...and no, you won't make partner. It is virtually impossible to make partner at Cravath. It isn't because you aren't qualified or competent, it is just because they only make 1-3 people per class partner.
The only reason I can think of (aside from Prestige) to pick Cravath over another firm that you fit better at, is for the marginally better exit options. Even this benefit has not been confirmed.
So go to Cravath is it is a good fit for you, but don't go simply because it is Cravath.