Pros
Pay is competitive with the industry, though is likely to flat-line year-on-year. Employment is usually secure, though ultimately depends on how one's face fits. Work/life balance is good. Most colleagues are decent to work with. A good place for those back office employees no longer needed by the banks as DTCC (incorrectly) regards this as the required skills set.
Cons
An excessively political environment where the emphasis is on 'playing the game' rather than doing one's actual job. The lack of commercial thinking at all levels has led to a litany of high-profile failed initiatives over the past decade. The pre-eminence of Operations people at the heart of DTCC has led to a back-to-front culture whereby those closest to the clients have to justify their existence to Ops people. Career progression is based on ingratiating oneself with management, which has led to a preponderence of weak, deferential stooges running the show. Those with charisma, innovative ideas, and who speak the truth are invariably managed out. DTCC makes all its meaningful decisions out of the US leading to a US-centric thinking and poor morale in other regions. The US-driven politically-correct environment (policed by HR) drives some to distraction.