Pros
The best reason for an industry analyst to work at Forrester Research is that it ramps up your visibility, brand, credibility, and connections in the industry, which is an asset you can definitely monetize through a range of opportunities elsewhere after you leave Forrester. Also, the pay is fine.
Cons
The chief downsides of working at Forrester Research are that it seems to be engineered to burn analysts out through continual overscheduling, overloading, distraction, marginalization, and disrespect. The management culture is dominated by a Cambridge-based clique of people who've been there forever, concoct lame company-wide themes, reorganize the place continually, focus more on sales numbers than the actual quality of published research, fail to recognize great work, promote themselves as analysts when they don't actualy do the research themselves, tend not to read the actual reports that their actual analysts publish, look down on research areas that may not be their personal favorites, skew opportunities (speaking, books, consulting, etc.) to their pet analysts, understaff the analyst teams severely, fail to respect the significant brand recognition that many analysts have gained in their respective areas, deny analysts the latitude and autonomy to define their research agendas as they see fit, and treat experienced analysts like they were lackeys.