You will work yourself to death and that is expected and you will have very little work-life balance. Be prepared, during the courting/orientation process they make a big deal about "work-life balance", but remember you are going to a professional services firm - it is all about billable hours. I recall one director mentioning that you will not get promoted unless your utilization is around 120% - which means you need 2400 billable hours per year (billable does not equal working hours, actual hours will be in the 3200-3400 range). So unless you want to be working 65+ hour weeks, week after week, reconsider your option.
Mergers and acquisitions sounds a lot cooler than it actually is when it comes to consulting. During the M&A process, bankers run the show and consultants are along for the ride. And unless you are in the financial due diligence area, none of the work you do will make a difference in the transaction, so the feeling of importance in what you do diminishes greatly.
During the staffing process, there is little consideration given to what you want to "work on". Basically, a partner sells a job, picks a director to run it and the director asks if you are available. If you are, you are staffed...and if you don't accept the gig, that is the fastest way to ruin your reputation.
Consulting consists of Powerpoint decks, making stuff up and saying whatever the customer wants to hear. Once the customer figures out he/she can do what you are doing for a lot less $, they will show you the door. Remember, you are hired hands, and when your manager/client sees no value add for the huge sums of money you are charging, they will have no problem ending your engagement.
The firm is extremely outdated when it comes to technology. The firm utilizes Lotus notes for email and IM communication. They are in the process of moving to Google this year, but it is still very embarrassing when you cannot sync up with your clients, all of whom use Microsoft Outlook.
They have a new method of performance evaluation, so during each engagement you are supposed to solicit feedback from your manager for a more "well'rounded" view of your performance. Most of the people reviewing you are on power trips and have no issue tearing you apart for the smallest mistakes based on some vague framework. These evaluations are the equivalent of getting a getting a hard-hitting yearly review every two weeks. Let me say, those can be extremely rough (even if you know you performed well, it is all based on that reviewers mood/perception).