Pros
Great corporate history and mission, heavy on scientific/environmental, expanded into Europe, now emphasizing Federal contracting, but non-DOD -- a good thing, if that tracks with your values. A company with a small-time feel, trying to grow up. There are always trade-offs in this phase, but ICF seems to be trying hard to keep their employee focus. See caveats below.
Cons
No preparation for unwary staff on the difference between being a consultant and being an employee. There is a big difference. You must please your client first or you will not last long. As a result, ICF has lost lots of great staff. ICF could do much better at this. Don't let your clients run your company for gods sake. It's death in the long term. Sometimes a company must say no to the client -- for everyone's benefit. But, hey, thanks for listening....