1. Cheap
2. Low pay*
3. High Attrition rate
4. Not a pleasant Work Environment
5. Stay away
*Unless you sell your day's off for $1000/day. Keep in mind that you will work like a slave and you will work hard for every penny of that $1000/day at a cost to your health and your time away from your family. Another benefit is that your taxes are paid for in Japan (carrying over to your country of residence) and that you are a Bona-Fide Resident with employment/resident status in Japan. In the end though, you'll realize that even with these benefits, it's not worth it.
Otherwise, you pretty much nailed it.