Avantages
Extremely receptive to hiring people with only academic experience (i.e., fresh out of grad school), which can be a great alternative to those considering post-doctoral work. You'll get a greater variety of work than you thought possible, and have some big brains to bounce ideas off. Something approaching "fun" may ensue. The pay is reasonable. Entry-level employees can get massive overtime.
Inconvénients
Not a particularly helpful or supportive work environment. A fellow employee (or even your boss) will gladly throw you under the bus to save themselves if you share a mistake. No orientation, no actual "managing," little praise or encouragement. The fight for billable work and credit for bringing in clients can make for a tense atmosphere, especially between the more junior and more senior staff, but also for those of equal rank. You are only as good as the amount of money you are bringing in, and little time is afforded for you to learn your job before high expectations are placed. Taking time off (even a personal day) is begrudged and counted against your annual billing quotient.