Pros
In my ten years at ICF, I worked with some very smart and passionate people who truly cared about the work they did. I was lucky to be in a group that allowed work from home flexibility, and until the last two years of my employment, felt challenged in my work.
Cons
As many reviews note, your ICF experience will depend a lot on your LOB and your manager. Unfortunately for me, poor management and an inability to grow in my career caused me to leave. In my ten years there, I had 7 managers, many of which were great, but the last manager is what drove me to leave as this person was completely immature - cursing loudly in an open office, talking about coworkers behind their backs, drinking to excess at networking events, disappearing for days - and wholly unqualified. I didn't want to be associated with this behavior. I also had hit the ceiling with career growth as my work had become stale and routine, and I had become very frustrated with receiving excellent reviews, but being told I couldn't be promoted because there was no criteria for promotion for the specialized work that I did. I also would encourage people to not believe ICF when they say salaries are competitive. I was able to increase my salary by $30K, just by going to another company at the same level, to do the same work. The hiring manager at my new company actually commented on how low my ICF salary was.