Pros
Flexible hours, pays on time (often early), if you make a mistake on an invoice they'll still pay what they owe you. Regular pay raises, but...
Cons
You're not really there to teach English. You're there to sell classes. You can get great student reviews by heaping praise upon students and the office will love you. Horrible, horrible support from the Boston office. If you have an emergency and follow procedure, they will still mark you as not showing and you can lose a week's work. You get regular pay raises -- but you also get fewer scheduled hours after you get that raise. People assigned to review you can't manage to do it in a reasonable amount of time. 1 minute late could cost you a raise. Many of your "colleagues" that you'll never meet are unprepared or unqualified.