Pros
You could potentially learn a lot quickly. Co-workers are great. You'll gain experience writing reports.
Cons
Compensation is very low. The learning curve can be steep, but then stagnates. There are rare occasions when senior staff know more technical skills (e.g. statistics, project management, data collection/analysis, etc) than associates. Which is very problematic for evaluation associates fresh out of graduate school who are still looking to develop their skills. After about 6 months there is little left to learn. Almost no internal promotions. A lot of Associates were promised Senior Positions within a year of their start data, and then we were told it was no longer an option. The CEO/owner can be very inconsiderate. Her primary function is to proofread reports. She has little qualitative and quantitative analysis skills, and limited knowledge of evaluation theories and best practices. Almost all of the work is limited to asking participants how satisfied they are with programs and comparing means. There is little critical though about effectiveness. Any statistical skills will go to waste. Turnover is extremely high.