Pros
Orchestrade has a relatively flat organizational structure, so, if you can take the initiative, there are opportunities to work on some very interesting projects, with high-profile clients across a wide range of business models and asset classes. The core software solution is, in parts, among the best in its class, and you'll be working with very some very smart and experienced people. Work/life balance is good, though the work can be stressful.
Cons
The flipside of the flat structure - internal organization can be a little chaotic. People's technical skills are frequently better than their communication skills, which can be frustrating. The system is relatively well-developed, so don't expect to be working on greenfield projects all the time. Much of the codebase is sparsely commented, with little standardisation of code style.