Vantaggi
There's always something new to learn, no longer how long you've been in the field. There is the opportunity to work with clients, in various methodologies (phone, IVR, web, mail, person-to-person) and combined methodologies. There is the opportunity to move in and out of technical work, project management, etc. and it all works together so there is no "wasted knowledge." You can take everything you learn and apply it to the next position you decide to pursue.
Svantaggi
Location (if you're not near the city) - the train schedule is inflexible, so if you just need 5 minutes to wrap something up you either let it hang or wait for the next one. If you don't have strong boundaries it is easy to be taken advantage of. Even when you get to the point where you have earned a lot of vacation, it is difficult to take it (depending on who you're working with).