Pros
My experience is that Citigroup appears not to be a serious employer. You can apply for a position with this company for which you are extraordinarily well-qualified, and you will NEVER hear back from the company. You will, however, continue to see the same position advertised by them, week after week, month after month, for a year or more after you have applied.
Cons
I work in Baltimore and I applied online for a long time before I actually started getting called. I think Citigroup is one of those companies where they have to post jobs even if they've already decided someone else is going to get it. I used to think that the applications led to a black hole too. It can sure seem that way and for other sections of Citigroup that might be the case