Pros :

1) you have a job,

2) you get paid

3) if the employer is legal and that you fulfill the requirements for such a teaching position, you get your visa

Cons:

1) it's one of the least regulated industry in China. Despite official guidelines, every school wants to hire a foreigner to teach English, but sometimes they are not authorized to do so, therefore you may get many problems when dealing with your visa or renewing your visa, or if the school doesn't want to pay you.

2) you don't really evolve in your career, except if you plan to be a teacher back home

3) you're very dependent on the school which can arrange your working time, your schedule at will

4) the most important is that if you teach in China just to get some money the time you're here, then why not. However, if you plan to stay a long time in China and keep a teaching job for several years, back home, no companies will be interested by your working experience as a teacher, except maybe private schools or teaching-related institutions. Many foreigners are happy with a teaching position, because the salary is usually good and the conditions are also good. But again, back home, depending on your age, your experience in China as a teacher is close to nil.

  Of course they're worth doing. A job is a job and for a foreigner in China, teaching is a pretty good job. You just have to read your contract 'very' carefully. Don't assume anything.