Avantages
Flexible about working from home, or even from another city. Fairly laid back environment. I hear it's easy to move between projects and offices. I also get the sense that things vary a lot between projects and offices. Company stock share plan that is matched 50% up to 2% of salary. Reasonable vacation time, as well as other personal leave as needed. As mentioned below, sometimes things are very slow. During those times there is flexibility about coming in a bit late, leaving a bit early. There is a social club, and their events tend to be worthwhile. Many of your co-workers will be fairly young.
Inconvénients
Variation between projects can be frustrating. Some teams have very little to do, while others are putting in 80 hour weeks. If you're not working from out of office or traveling, you will be working in a cube. Some technical consultants end up in relatively un-technical roles. For example, developers who do very little coding and spend most of their time support existing systems, upgrading third party software, etc. Working mainly or exclusively from home can be a drag, and some complain of missing personal collaboration with their team. Sometimes management's expectations are unclear. Sometimes the laid back attitude leads to simple tasks taking longer than is necessary.