Pros
*Internationally mobile career in great cities. Prep Zone is in Dubai, Singapore and even Shanghai now.
*Work with really smart people (it's test prep - these guys all have 2300 SAT and 760 GMATs)
*After a year of intensive teaching, which can get redundant, there are a lot of content or sales/marketing stuff you can get involved with.
*Many times you will have a lot of responsibility very early - great for your resume but a lot of work
*Potential for decent pay after first 6 months or year
Cons
Company is growing so fast that roles aren't well defined and things can get sloppy
Certain people involved in sales have too much power in the organization
Teaching test-prep can get boring but if you're doing grad level stuff and interacting with GMAT or GRE students this is less of a problem.
Starting pay can be a bit low but you tend to make more after 3 or 6 months