Pros
Working for Propeller can be extremely rewarding, in that: a) the firm maintains a diverse portfolio of clients across industries with challenging business needs, and b) you get to work with whip-smart, interesting (and different!) people, and build your network through fun and engaging work - which can be either client-facing or internal. There can't be many better places to get exposed to new industries, new methodologies, and develop your skill set.
Kontras
Work at Propeller grants consultants a high degree of autonomy, and at times you can feel like you're on an island tackling a complex problem. Also, this hasn't been my experience, but I've talked with colleagues who have found themselves in a "dull" engagement where consultant-level expertise may not have been needed. But this seems to be the exception, not the norm.