These reviews are for Slalom Boston and I believe each office operates little bit differently.
Pretty much 70% of the consulting engagements are staff augment / temp staffing type assignments. You are by yourself at the client with little to no support except when role is being extended or opportunity for potential up-sell.
The client engagement staffing is poor and is based on available roles (demand) and available people (supply) rather than skills and experience match for the role. If you were an experienced PM before you may end up staffed as junior BA in a long term client project or if you are not an IT person and you might end up in an IT project. And you are stuck there for a long time doing things you do not like.
Most of us end up as perpetual Consultant (job title) - no meaningful upward career trajectory. There are many many "consultants" who have been around for a 3+ years without any potential for upward movement and many people who joined 3 years ago or before have left the company.
Internal leadership roles are filled by hiring from outside rather than grooming and promoting the experience staff.
When you joining Slalom, they may match / even pay little bit more than your current salary, but once you are in your annual increase and bonus are are very very small (3 - 4% a year at the most). And you are expected to do lot more than your client work to crack the 5% mark (with at least 10+ hours a week).
Not a great option for experienced consultants - for instance if you are a Sr. Consultant, Manager and above in any of the major consulting firm, then you will feel very much stuck in Slalom.
The job titles are not very industry standard and comparable to others. The job titles in client services are: Consultant, Principal Consultant, Consulting Manager, Solution Architect, Solution Principal, Practice Area Lead and Client Services Lead. You are told that this is not linear and you can go from any title to any title. There are couple of people who used to be "Directors" in other firms joined Slalom as consultants and they have been "consultants" ever since. They are at the bottom of the pile with everyone else.
If you were to compare to Accenture, Deloitte or PwC consulting titles: Principal Consultant and Consulting Manager is equivalent to "Manager" in Accenture; Solution Principal and Solution Architect is equivalent to "Senior Consultant" or Manager in Accenture and the only difference is you are specialized in certain area (example Project Management).
Poor leadership - During the hiring process you are told Slalom is entrepreneurial and you can make your own career, flat organization, etc., but in reality there is a ceiling you'll be stuck under and if you stay here many years you career will stall and you will not be marketable.
There is lot of dissatisfaction among staff and resulting in quite a bit of attrition.
There is a general consensus that people have been treated poorly when they gave notice to leave the company.
Most everyone I know are looking for opportunities to jump.
Poor benefits.