Pros
The majority of people is friendly and supportive, Forrester promotes a culture of collaboration and camaraderie. You will find that they are open to all ideas independently of your role in the company, therefore, since the beginning of your employment, you can add your two cents to the discussion if you have something worth saying. Life/work balance is quite good with some punctual peaks of "too much work" from time to time. If you are curious and smart, I totally recommend this company.
Cons
Long distances and time differences don't make things easy sometimes, it's not unheard of people from non-US offices feeling a bit disconnected from the HQ. Having said that, they are actually working hard to create more seamless communications between all offices. Some strategies and objectives that are tailored for the US are not fitting for EMEA and APAC.