Pros
The people make it worth working at Mercury Z. If you want to work somewhere that the company culture is completely influenced by the work people are doing every single day and how those people relate to each other, then working at Mercury z isn't so bad.
Cons
If you want to grow in your career or move forward, you may not be able to. You may find that you have been stuck in a rut because it's where they see you as best. It may not be where your talents truly are. Management works on a need to know basis and most times they don't think you need to know, even when they are planning a big change.