Pros
You get to know lawyers with elite credentials
There is a bit of a "we're all in this together" vibe because of how disorganized and vitriolic firm management is
Work/life balance can be quite good for weeks at a time (before you get abruptly asked to stay up all night several days in a row with no notice)
Cons
Most partners are haughty and short-tempered and view associates and legal assistants as fungible.
Pay is terrible, given how disruptive the job can be to your personal life. You can be required to work overtime -- which might mean staying up virtually all night for several days in a row -- with no notice.
Most cases are understaffed, so the above scenario is quite likely.
Work is extremely boring and monotonous because legal assistants are not allowed to do any real analysis.
Despite this being an elite firm, most associates are cynical and burnt out. Their negative outlook on life can draw you in.
The job is a complete dead end. Experience as a legal assistant does nothing for you in the corporate world, so by taking this job you basically are backing yourself into a corner where you have to go to law school or just get another entry-level job (which will be harder to get now that you've entered the workforce, than if you just did this straight out of college).