Good for someone, bad for others

I did JET 2005-2007 in the southern part of the main island. I had a great time as an elementary school teacher with only 4 junior high days per month, but it was a lot of work. If you go into JET without any teaching skills or experience in K-12 classrooms, you will be getting a crash course, and if you have minimal or no Japanese, you will probably have a rough time in your personal life, even if you can get by OK at school.

If you DO have teaching experience, it's both a curse and a blessing. On one hand, you will be able to make lesson plans, have a good sense for the pedagogy appropriate to the age level, etc. On the other, you will be working within a system that may not want your expertise, or with a teacher who lacks all enthusiasm or ability. These can drain you if you aren't prepared to find entertainment and satisfaction in the students, outside curricular activities, or your personal life. You also may want to come with a nice little nest egg of at least US$1,500 to get yourself started, as you may not be paid for several weeks and may need to buy stuff for your apartment and pay for food until then.

I recommend JET to people who have some ability with Japanese and willingness to keep learning the language, who are adventurous and enjoy traveling and could live in rural or suburban areas, and who are generally cheerful/friendly with strangers and OK with touchy-feely kids. I do not recommend JET for people who have medical issues that may be tough to treat in Japan (several friends had to quit early due to this), people who aren't prepared to step back and take a neutral look at bad situations/cultural clashes, or people for whom being a virtual "camp counselor" sounds horrifying. If you are bringing a spouse along, it may be hard for them to find a job, so please take it into consideration.

That said, I had a blast, taught over 3,500 kids in 2 years, and had classes ranging from 4 kids to 120 kids at one time, and I loved inventing new games to get them excited and hanging out with them on the playground or after school. I also loved traveling around the country (I had 20 days' vacation + national holidays) and taking part in local events and festivals with my students.