Pros
Once you pass the online personality profile and prove yourself personable, persuasive, performance-driven (pick any pair, at least) but always polite, on the phone, you're in and you can make decent money - even good money for this kind of work - especially when you consider that you aren't asking people to buy anything, just give their opinions. The Gallup name still carries enough good will that some people will talk to you for the name alone. Flexible hours. Tuition assistance program. The transgressions for which an interviewer can be terminated are very clear and usually easy to avoid. Most of the interviewers I know who have been fired knew they deserved it. A clear path is provided for you as an interviewer to improve your pay scale and bonuses do help. There is a chance for promotion to management positions or a place in the corporate office, especially if you're an attractive, young, female UN Lincoln graduate or related to someone in the inner circle (in which case, you aren't reading this anyway). If you perform well and act like you want to participate in the culture - and culture is EVERYTHING here - they'll make it easy for you to continue. Even if you don't perform well right away, they'll try to help you improve - and some people do. But some people don't or can't or won't. If you can not make yourself fit in, they will make it easy for you to decide to leave (but do try to stay at least six months so you can list them on your resume without fearing they'll tell prospective employers that you are not eligible for re-hire).
Cons
You must be willing to learn how to deal with rejection and to speak politely and effectively with rude and/or stupid respondents. This type of work is not for everyone. Your success will be determined largely by your willingness to submit to a Borg-like "tribal" culture. They expect you to love them without reserve while they reserve the right to terminate you at will.