On the positive side:
Learn about different cultures
Learning about more than one culture and more than one language enhances your knowledge. There is more than one way to eat, drink, pray, celebrate, negotiate, socialise, perceive and interpret the world
Become a seasoned traveller
Working abroad mostly means a lot of travel in a foreign place. You get to see the world while earning money
Learning languages
Every language is a universe of its own. Learning, how other people express themselves means learning a different perspective on the world
Cross-cultural awareness
Lear how to team work with people of different background
And that also means: Improving your communication skills
Crank up you CV
International experience, especially early in your career helps you stand out from the crowd and may give you better chances to promotion
On the negative side:
Lack of stability
Moving far away from family and friends may mean phases of loneliness. For most that remains a phase, but still, international careers can cause a lot of moving and up-rooting
Culture shockEvery country is different. Having to manoeuvre different ways of working, negotiating, adhering to hierarchies etc. can be time-consuming and stressful. Particularly in the early stages of a stint abroad
Living conditions
Especially if you start work in an emerging country, the standard of living, the taste of food and the climate may be very different from what you are used to at home. Some countries even may have safety issues
Information overload
Apart from having to learn a new language and new patterns of behaviour, every country has its own rules and norms of working. Some people find it hard to adapt to so much change in a short time frame
Career issues
In many international corporations there is a lot of fluctuation and there is no guarantee that you will be relocated at a post on the same level in the next country. Salary and tax levels may change as well, also consider cost of living. Sydney is more expensive than Dublin, to work in compliance in Zurich might mean something very different from working in compliance in Lagos