Pros
Getting to work on very complicated infrastructure helps you develop best practices and implement root fixes
Cons
Almost everything, things are so poorly done and you're pushed towards keeping touch with the customer while not providing real fixes just to keep to SLAs, not to mention that 1st line issues bleed into 2nd line and with a non-existing t 3rd line, you're tasked to identify and fix very complicated issues that would take a lot of hours to fix due to unfamiliarity of the infrastructure, caused by lack of up-to-date documentation and a toxic team-culture that encourages back-stabbing so they can pass very rigorous probations, everyone in order to meet all targets has to work overtime in the service desk, paired with poor management and lack of accountability on their part and identifying the root cause of issues, they simply put everything on the service desk hiding behind documented and poorly created processes that can't be followed to a tea, with encouragement to deviate from the processes while punishing you when you do so.
Honestly, it's the worst tech company I've worked for. Management took systems from large companies with a lot more resources and very structured systems and implemented in a very small company that doesn't have those resources, making everything extremely difficult to get done and without the support required to execute on these processes.
Avoid at all costs.