Pros
To be fair there are many benefits to working for a Big Four accounting firm. You will learn a ton of new information and you will grow as an employee. Employees get to work with many talented people. Not to mention a job at a Big Four looks great on your resume.
Cons
On the downside, if you look at the Best Places to work lists - you will find KPMG either listed below every other Big Four firm or completely absent from the list. Top management can make all the excuses they want but it comes down to two primary issues. Management loves to take credit for success but blames underlings for failures. Either way you aren't going to share in the money pouring into the firm. Second, management likes to play favorites and no one seems to be willing to reel these managers in. Companies need to be able to show why one employee was promoted over another and in many cases a halfway good lawyer could prove that this was not the case. Over the years I watched countless talented employees jump ship to the other Big Four Accounting firms. As a result, many people who do remain and work up to Partner or Principal aren't the best and brightest. The few fantastic partners/managers remaining have a very long list of employees trying to get into their group. If you find yourself working for this firm and want anything other than a very, very slow climb to the top - take as many classes as you can and constantly look for a position at one of the other Big Four Accounting firms. Many people I know jumped ship with their manager to a new firm and even entire departments have left together. After working one too many 100+ hour work weeks for this firm I left and I would argue that any firm that loses an entire Practice group to a competitor - isn't some place you want to be long term.