Pros
The essential asset Forrester has is its people. The company is populated with with very smart, reasoned people. Most have both strong academic backgrounds together will successful practitioner experience. The company is well respected and treats its clients like gold. Forrester delivers on what it promises, both internally and externally. Even with a staff of over 1000 people there is very little office politics and associated drama. Again, this is a product of having mature and competent hires. Although much is expected and the work is rigorous, there are always strong rewards for performing to plan - both personally and professionally.
Cons
Long hours are required, this is not for everyone. High levels of competence is required at all times. The company does not offer dogma and contrarian thinking is encourage. But again, this is not an environment for the uninspired. Average energy and average ability folks will feel uncomfortable here. For some positions the demands make work/life balance harder to manage then some firms. The company does a great job at providing all of it's employees with the technology and tools to take the mechanical tasks away - or at least minimize - from the day to day. This is work only fitted for self starters.