Pros and Cons
of JET
PROS
Work with children - For those of you (like me) who are destined for careers completely unrelated with children, this is a rare and very beneficial experience.
Pays well - Particularly for ALTs, for a job that only requires English fluency, a college degree and doesn't mandate many responsibilities upon you, this pays well.
International work experience - This goes particularly for CIRs, but for ALTs as well. To those of you wishing to go on to graduate school, this experience is quite desireable.
Travel opportunity - To see not only Japan, but surrounding Asian countries, as well as the rest of the world. School vacations allow for such travel, but even CIRs can manage to pull off overseas trips. Discount agencies like H.I.S. make rather elaborate vacations affordable (I managed a round-trip 1 week SCUBA diving tour in Thailand for a total of $650!!!)
Interact with people from around the world - This is of course true of the Japanese people around you, but also with your fellow JETs and the people you will meet on your journeys.
Learn the language - No way to learn a language like being in the country itself.
Nice to be a man (women please wait for the cons) - Not that it is all fun and games for overseas men, but if you consider the romanticized image of the West, combined with the social value attached on using English and the Japanese male's general inability to adapt to the self-empowerment of a new generation of Japanese women, and you have many international couples forming.
Buy time - Nothing like taking 1-3 years to reflect upon what you want to do and where you want to be in the future. Also offers a good opportunity to further personal endeavors which you may not have the chance to pursue once back home.
CONS
Far from home - Obviously, most of you won't have your family and friends with you in Japan. This can be particularly trying for people with very close relationships , particuarly for those who can't speak the language and are outside of the city.
Transitional relationships - You will encounter many other teachers who only plan on spending only a year or two in Japan, thus limiting the degree to which they become emotionally involved with others (Then there is the opposite, those who cling to their surrounding JETs for dear life, explaining somewhat why there is so much JET intermarriage).
Exposed to financial markets - You have entered the market upon entry here, whether you like it or not. The yen is strong, the yen is weak, the flow of the dollar/pound/etc...Timing is everything. Need to study up to pay off your loans or send money home efficiently!
Tough to be a woman - Times may be changing, but it is still much more common for overseas men to find a Japanese girlfriend than vice versa. Japanese women are considered to be more passive in general, compared to women from Western nations, so many Japanese men are intimidated by foreign women. Doesn't mean you have to become a nun, just that you should know the dating environment before coming to Japan.
Culture shock and reverse culture shock - Depending on where you are assigned, it may take some adjusting and some things may be rather unberable at first. I would argue that the reverse culture shock is particulary true for those who deeply involve themselves in the Japanese culture. I always felt that the reverse culture shock was worse, because I was in a city area with access to most of what I had back home.
SUMMARY
At the risk of being redundant, I should point out that pros and cons are a matter of perspective. What I have written as pros may be considered cons by someone else. I have simply taken the liberty of offering my own perspective.