Vantaggi
Good office facilities, cafe and beverages, snacks - these are constantly the same so at one point you no longer like them. The opportunity to work with smart engineers (emphasize on engineers, because not all managers are like that) using latest technologies.
Svantaggi
There are few hypocrite managers which believe they can "influence" all other with their incorrect behavior. The opportunities for promotion are not equal to all employees - there are few employees who are regularly promoted - let's say every 2 years without any strong justification for that. At the same time people with strong technical contribution are intentionally stuck on low levels and eventually smart engineers either leave the company or are managed by inadequate "fast-promoted" managers which actually devalues the process. The situation in Bulgarian office unfortunately is as in the whole Bulgaria -not transparent, corrupted, "friends-only" fake promotions.