Pros
For me, the culture really makes it - everyone is incredibly supportive and we have fun, yet also get the work done. No-one is afraid to get their hands dirty and get stuck in to something if you need help or there's a looming deadline. It's fast paced and perhaps not for the faint-hearted, but the people really make it. Every day there's something new, with a diverse range of clients and projects to get involved with. The flexibility works particularly well for my lifestyle, as I can fit other commitments around work to suit me. I'm a little further away from HQ than other members of the team so I visit the office less than others, but I don't feel any less connected to the team.
Cons
As with most agencies, it can be mentally demanding at times due to the pace of work, although it comes in peaks and troughs dependent on deadlines.