Pros
After my initial adaptation period, I started seeing how things work in the firm. Almost everyone does something useful, and all I have dealt with so far know what they are doing pretty well. Most people are pretty intelligent, and some of them are really fast at what they do to get your needs served.
The organization is a pretty flat structure and (somewhat) friendly. Aside from the managers, everyone is at work producing something that contributes literally to the code that runs in production.
Management appears to be not standing in the way. To the contrary, they try to help you by understanding your needs, and attempt to solve them as quickly as they can. The CEO is always reachable, and walking on the floor all the time. You can get your concern out to him, and he will help you. He is pretty transparent about the health of the firm, and provides quarterly reports to employees.
HR has been trying hard to increase the interaction among people from all disciplines - traders, developers, network people, IT, compliance, legal, etc.
As long as you do your job, and/or (if you are in that position) bring in money, you are pretty safe.
Quarterly bonus, daily free breakfast and lunches, weekly free massages, free food and beverages outside the breakfast/lunch time, fun company events all around the year. Did I mention all free?
Overall, it's a great place to work if you like working (hard).
Cons
Not that I can see so far