Before joining a Big Four audit company, I read a Corporate Research Foundation survey that rated them one of the best companies to work for in the world. I remember mention by this survey of the "rapid mobility" afforded to employees of this firm as a plus.
Professional services companies deploy staff to various client locations around the country they operate in. As a consultant (an auditor in my case) you need to be at the client to understand, analyze and improve their systems and controls, report on their financial statements, or rectify a system problem they may have hired you to fix. Working from your company's office is the exception rather than the rule, reserved for times when you are concluding your findings into a report or when you're not assigned to a client.
Those words "rapid mobility" have a glamorous ring to them, but there are details and realities of working for a consultancy that many people don't consider:
#1: You can be deployed to any corner of the country at one day's notice
This isn't an exaggeration: you can go in to work on Monday and be informed that you are leaving to a little known area 800 kilometers away on Tuesday. You must be prepared to pack up and leave at very short notice. And bear in mind you aren't always going to be sent to Tokyo or Prague: Clients can be in the most desolate places and often you need to drive there rather than fly.
#2: You need to fill in a timesheet
When you work for a firm that charges its time out, often you're squeezed to work overtime and not charge it. Managers will convince you that you're working overtime not because your workload is high, but rather because you were inefficient -- they have a budget for each job and client to watch. Justifying your existence on an hourly basis and fighting for billable hours is probably the most frustrating and demoralizing part of working at a professional services firm.
I've seen many people leave "boring desk jobs" for one of these consultancy gigs, only to regret their decision a month after starting their new job. Going to work and clocking your card for a set amount of hours is usually hard enough, but working at a professional consultancy adds in the need to justify what you do with each hour of your day. Even when unassigned to a client I had to fill in what I did each hour.
When I subsequently became a buyer there was also some travelling involved when I had to visit suppliers, but while I had an agenda to close for each visit, I was never filling in a time sheet. Anything not resolved at the visit could be continued over phone or email. Often when auditing there would be information, reports and audit sections that had to be completed while on site at the client - you had to get things live from their system at a certain point in time and not via email. It can feel as if there's a big clock ticking above your head.
#3: You work, you don't sight-see
Travelling on holiday is fun. Travelling on work sucks. You have a limited time period to complete your work when you're away. It's good to get away from the office occasionally, but sleeping in a strange bed and eating fast food is unsettling for all but the most outgoing of people. The novelty of travelling wears off very quickly when it's for work.
I didn't create this post to bash any professional firm; I just felt that my experience would be useful to someone who is contemplating life in a consultancy as opposed to a "normal" company.
To summarize: It's not for everybody, in fact, it's not for most people. You need to be comfortable with going places at short notice and be someone that isn't too attached to their home and family if you are to find some satisfaction in consultancy.