Pros
The great people - truly intelligent and people savvy. I've worked at several companies (both in industry and through consulting) and have found that Accenture is truly unique in how it's able to manage 180,000 people. The internal knowledge sharing at Accenture is also stellar compared to other companies I've worked for (and also compared to other consultancies from what I've heard through others). Additionally, the ability to work in different industries and in vastly diverse roles (dependent on how aggressive you are at networking) is also a great reason to work for Accenture. Hands down, I would return to the firm if given the chance.
Cons
Long hours, long hours, long hours. The work/life balance at Accenture (and is just the dogma of consulting) is non-existent. When you have a deliverable that's due, you have to burn the midnight oil, lose your personal life, and age beyond your years. Since there are so many intelligent, type A people at Accenture, it's hard to come out as outstanding during review time. Even though you may be a mega superstar on all your projects you may come out with just a meets expectations rating at year end review. It's definitely a hard concept to digest - knowing that you're working for peanuts (but you do get awesome experience!)